🌍 How To Calculate Soil Volume For Pots
You're calculating soil volume for a single houseplant repotting, determining the pot's actual soil volume in 5-gallon nursery pots, calculating Volume in cubic feet for commercial operations, planning soil volume for landscape projects, or determining pot specifications for various nursery containers, this guide helps you make accurate calculations and purchases.
✓ Diameter = top opening width (for round pots)
✓ Always round UP when buying soil
✓ Leave 2–3 cm from soil to rim for watering
Medium bags: 5L ($3–4) — Common choice
Standard bags: 10L ($5–8) — Most popular
Large bags: 20L ($10–15) — Multiple pots
Bulk bags: 40L ($15–25) — Gardens, contractors
Bulk (loose): 40–50L ($20–30/bag) — Best value
PRO TIP: Buying one 20L bag vs two 10L bags often saves 10–15%
• Round: 15–18 cm diameter × 20 cm height
• Square: 20×20×15 cm
• Soil needed: 5 litres
• Best for: Herbs, small flowers, succulents
MEDIUM POTS (10 litres):
• Round: 22–25 cm diameter × 25 cm height
• Square: 25×25×20 cm
• Soil needed: 10 litres
• Best for: Vegetables, medium flowers, young plants
LARGE POTS (20 litres):
• Round: 30–35 cm diameter × 30 cm height
• Square: 35×35×25 cm
• Soil needed: 20 litres
• Best for: Tomatoes, peppers, shrubs
EXTRA LARGE (30+ litres):
• Round: 40+ cm diameter × 35+ cm
• Square: 40×40×30 cm
• Soil needed: 30–50 litres
• Best for: Trees, large plants, specimen
| Pot Type | Diameter (cm) | Height (cm) | Volume (L) | Best For |
|---|---|---|---|---|
| Small Round | 15 | 20 | 3–5 | Herbs, succulents |
| Medium Round | 22 | 25 | 8–10 | Vegetables, flowers |
| Large Round | 30 | 30 | 18–20 | Tomatoes, shrubs |
| Small Square | 20 | 15 | 5–6 | Herbs, flowers |
| Medium Square | 25 | 20 | 10–12 | Vegetables, shrubs |
| Large Square | 35 | 25 | 25–30 | Large plants, trees |
• Peat moss or coco coir: 4L (40%)
• Perlite or vermiculite: 4L (40%)
• Garden soil/compost: 2L (20%)
• Cost: ~$7.50 | Drainage: Good
RECIPE 2: VEGETABLE MIX (10L)
• Garden soil: 5L (50%)
• Compost: 3L (30%)
• Peat moss: 2L (20%)
• Cost: ~$6.00 | Nutrients: High
RECIPE 3: SUCCULENT MIX (10L)
• Cactus soil: 5L (50%)
• Perlite: 3L (30%)
• Compost: 2L (20%)
• Cost: ~$8.00 | Drainage: Excellent
RECIPE 4: SEED STARTING (10L)
• Peat moss: 5L (50%)
• Perlite: 5L (50%)
• Cost: ~$9.00 | Aeration: Excellent
FOR DIFFERENT VOLUMES:
• 20L batch: Double all amounts
• 5L batch: Use half amounts
• 30L batch: Triple all amounts
✓ Prevents waterlogging
✓ Improves root health
✓ Prevents compaction
✓ Extends pot lifespan
2 cm gravel layer reduces soil volume:
• Small pots (5L): ~0.3L reduction
• Medium pots (10L): ~0.6L reduction
• Large pots (20L): ~1.2L reduction
• XL pots (30L): ~1.8L reduction
Materials for drainage:
• Gravel/stones (most common)
• Broken pottery/terracotta
• Perlite (lighter weight)
• Packing peanuts (reuse)
• Recycled materials
• Succulents, herbs (basil, parsley), lettuce
• Example: 20×20 cm square = 6–8L
MEDIUM ROOT SYSTEMS (25–30 cm depth):
• Peppers, eggplant, flowers
• Example: 25×25 cm square = 15–20L
DEEP ROOT SYSTEMS (35–50 cm depth):
• Tomatoes, larger vegetables, shrubs
• Example: 30×30 cm round = 25–35L
VERY DEEP ROOT SYSTEMS (50+ cm depth):
• Trees, large shrubs
• Example: 40×40 cm square = 50L+
• Potting mix: 0.3–0.5 kg/liter
• Garden soil: 0.6–0.8 kg/liter
• Peat-based: 0.25–0.4 kg/liter
WET SOIL WEIGHT (after watering):
• Potting mix: 0.6–0.9 kg/liter
• Garden soil: 1.0–1.3 kg/liter
• Peat-based: 0.5–0.8 kg/liter
EXAMPLE WEIGHTS:
• 10L pot, potting mix: 3–5 kg (dry), 6–9 kg (wet)
• 20L pot, garden soil: 12–16 kg (dry), 20–26 kg (wet)
✓ 40–50L bags: 20–30% cheaper per liter
✓ Buy at season's end (discounts)
✓ Buy with friends (share bulk)
MIX YOUR OWN:
✓ Use 60% garden soil (cheapest)
✓ Add 20% compost (homemade free)
✓ Add 20% perlite for drainage
✓ Cost: 50% less than pre-made
REUSE SOIL:
✓ Replace top 1/3 annually
✓ Add compost + fertilizer
✓ Sterilize before reuse (bake 1 hour)
✓ Saves 33–50% per year
FREE/CHEAP MATERIALS:
✓ Compost: Make at home
✓ Leaves: Free mulch layer
✓ Packing peanuts: Drainage
✓ Coffee grounds: Compost addition
Complete Soil Volume Calculator Guide for Pots: Nursery Pot Sizing & Soil Capacity
Master Soil Volume Calculator: Comprehensive Guide to Nursery Pot Capacity, Soil Volume Calculations & Pot Sizing
Understanding the actual soil volume capacity of standard nursery pots is essential for accurate potting, transplanting, and soil purchasing calculations. Whether you need to determine the Volume of a standard 5 gallon nursery pot for soil estimates, calculate the Volume of 8 inch pot in litres for houseplant repotting, understand what is the best estimate for the Volume of a small pot, find the actual soil volume capacity of #5 nursery pot in cubic feet, or need soil volume calculations for various pot sizes from 4 inches to 5 gallons, this comprehensive calculator guide provides all specifications and conversion tools.
This guide covers detailed soil volume calculations for standard nursery pots, actual soil capacity measurements in cubic feet and gallons, volume specifications for 6 inch nursery pot volume litres and 8 inch pot volume liters, complete nursery pot sizing charts with soil capacity data, 5 gallon nursery pot actual soil volume specifications, conversion formulas between cubic feet, litres, and gallons, mobile-optimized calculation tools, how to estimate soil volume needed for various pot sizes, and practical soil purchasing guides based on pot volume requirements.
Whether you’re calculating soil volume for a single houseplant repotting, determining the pot’s actual soil volume in 5-gallon nursery pots, calculating Volume in cubic feet for commercial operations, planning soil volume for landscape projects, or determining pot specifications for various nursery containers, this guide helps you make accurate calculations and purchases.
⚡ QUICK START In 60 Seconds
NEED SOIL VOLUME? ANSWER 2 QUESTIONS:
Q1: What size pot do you have?
- 4-inch pot → 0.5 liters (0.018 cubic feet)
- 6-inch pot → 1.5 liters (0.053 cubic feet)
- 8-inch pot → 3.5 liters (0.123 cubic feet)
- 5-gallon bucket → 15-18 liters (0.53-0.64 cubic feet)
Q2: How many pots?
- Single pot → Use soil volume for that size
- Multiple pots → Multiply volume × number of pots
- Bulk calculation → Add all pot volumes together
📏 Key Fact: Actual soil capacity = 85-95% of total pot volume
🪣 5 Gallon Pot: 15-18 liters actual soil capacity (not full 19 liters)
📊 Standard Rule: Don’t fill pots (allow 1-2 inches headspace)
🎯 NEXT STEP: Find your pot size in the Nursery Pot Capacity Chart
⚡ 5-MINUTE DECISION TREE
QUESTION 1: What is your pot size or type?
✅ Small pot (4-6 inches) → Use SMALL POT VOLUME SECTION
✅ Medium pot (6-8 inches) → Use MEDIUM POT VOLUME SECTION
✅ Large pot (10-14 inches) → Use LARGE POT VOLUME SECTION
✅ 5-gallon nursery pot → Use the STANDARD 5-GALLON POT SECTION
✅ Custom/unusual shape → Use CALCULATION FORMULA SECTION
QUESTION 2: Do you need actual soil capacity or total pot volume?
📐 Total pot volume → Full internal dimensions
🌱 Actual soil capacity → Accounting for headspace (85-95% of Volume)
📊 Best for purchasing → Use actual soil capacity (leaves room for water)
QUESTION 3: What unit do you need?
📊 Litres → Standard metric measurement
🪣 Gallons → USA standard measurement
📐 Cubic feet → Large volume calculations
📏 Cubic inches → Precise measurements
📊 NURSERY POT VOLUME COMPARISON AT A GLANCE
4-INCH NURSERY POT
📏 Diameter: 4 inches
📊 Total Volume: 0.65 liters (0.17 gallons)
🌱 Actual soil capacity: 0.5-0.6 liters
📐 Cubic feet: 0.018-0.020
💰 Price: $0.30-0.75
6-INCH NURSERY POT
📏 Diameter: 6 inches
📊 Total Volume: 2.0 liters (0.53 gallons)
🌱 Actual soil capacity: 1.5-1.8 liters
📐 Cubic feet: 0.053-0.064
💰 Price: $0.50-1.50
8-INCH NURSERY POT
📏 Diameter: 8 inches
📊 Total Volume: 4.1 liters (1.08 gallons)
🌱 Actual soil capacity: 3.5-3.9 liters
📐 Cubic feet: 0.145-0.138
💰 Price: $0.75-2.50
5 GALLON NURSERY POT
📏 Diameter: 10-11 inches
📊 Total Volume: 18.9 liters (5 gallons)
🌱 Actual soil capacity: 15-18 liters
📐 Cubic feet: 0.53-0.64
💰 Price: $1.50-4.00
PART 1: UNDERSTANDING SOIL VOLUME CAPACITY
TOTAL VOLUME VS ACTUAL SOIL CAPACITY
Key Distinction:
Total Pot Volume:
- Full internal capacity of the pot
- Measured from bottom to rim
- 100% capacity including headspace
- Used for pot specifications
Actual Soil Capacity:
- Practical usable soil volume
- Accounting for 1-2 inch headspace (drainage/watering)
- Typically, 85-95% ofthe total Volume
- Best for soil purchasing decisions
Why the Difference?
Headspace Requirements:
- Water pooling during watering
- Prevents soil overflow
- Allows for watering technique
- Prevents soil compaction damage
- Recommended 1-2 inches minimum
Example:
- 5-gallon pot total volume: 18.9 liters
- Headspace (1.5 inches): 3-4 liters
- Actual soil capacity: 15-18 liters
- Purchase soil for a 15-16 liter pot (not a full 19 liters)
SOIL VOLUME CALCULATION FORMULAS
For Cylindrical Pots (Most Common):
Formula: V = π × r² × h
Where:
- V = Volume
- π = 3.14159
- r = radius (diameter ÷ 2)
- h = height of pot
Example Calculation (8-inch pot):
- Diameter: 8 inches
- Height: 8 inches
- Radius: 4 inches
- Volume = 3.14159 × 4² × 8
- Volume = 3.14159 × 16 × 8
- Volume = 402.12 cubic inches
- Convert to litres: 402.12 ÷ 61.024 = 6.59 liters total
- Actual soil capacity: 6.0-6.3 liters (minus headspace)
For Rectangular Pots:
Formula: V = length × width × height
Example (6″ × 6″ × 8″ pot):
- Length: 6 inches
- Width: 6 inches
- Height: 8 inches
- Volume = 6 × 6 × 8 = 288 cubic inches
- Convert to litres: 288 ÷ 61.024 = 4.72 liters total
- Actual soil capacity: 4.2-4.5 liters
Cubic Inch to Litre Conversion:
- Divide cubic inches by 61.024 = litres
- Example: 402 cubic inches ÷ 61.024 = 6.59 liters
Cubic Inch to Gallon Conversion:
- Divide cubic inches by 231 = gallons
- Example: 402 cubic inches ÷ 231 = 1.74 gallons
Litres to Gallons:
- Multiply litres by 0.264 = gallons
- Example: 6.59 liters × 0.264 = 1.74 gallons
PART 2: STANDARD NURSERY POT SOIL CAPACITY CHART
SMALL POTS (Seedlings & Starter Plants)
4-INCH NURSERY POT
Specifications:
- Diameter: 4 inches (10 cm)
- Height: 4.5 inches (11.5 cm)
- Total internal Volume: 0.65 liters
- Volume in gallons: 0.17 gallons
- Cubic feet: 0.018 cubic feet
- Cubic inches: 40 cubic inches
Actual Soil Capacity:
- With 1-inch headspace: 0.5 liters
- With 0.75-inch headspace: 0.55 liters
- Practical capacity: 0.5-0.6 liters
- Fill level: 3.5-4 inches from the bottom
Best For:
- Seedlings
- Small succulents
- Herb starters
- Propagation
- Small rooted cuttings
Price per pot: $0.30-0.75
5-INCH NURSERY POT
Specifications:
- Diameter: 5 inches (12.7 cm)
- Height: 5 inches (12.7 cm)
- Total internal Volume: 1.2 liters
- Volume in gallons: 0.32 gallons
- Cubic feet: 0.042 cubic feet
- Cubic inches: 77 cubic inches
Actual Soil Capacity:
- With 1-inch headspace: 0.95 liters
- With 0.75-inch headspace: 1.0 liter
- Practical capacity: 0.95-1.1 liters
- Fill level: 4-4.5 inches from the bottom
Best For:
- Small potted plants
- Young houseplants
- Individual herb plants
- Single flowers
Price per pot: $0.40-1.00
MEDIUM POTS (Standard Houseplants)
6-INCH NURSERY POT
Specifications:
- Diameter: 6 inches (15.2 cm)
- Height: 5.5 inches (14 cm)
- Total internal Volume: 2.0 liters
- Volume in gallons: 0.53 gallons
- Cubic feet: 0.053 cubic feet
- Cubic inches: 127 cubic inches
Actual Soil Capacity:
- With 1-inch headspace: 1.5 liters
- With 0.75-inch headspace: 1.7 liters
- Practical capacity: 1.5-1.8 liters
- Fill level: 4.5-5 inches from the bottom
Best For:
- Most common houseplants
- Medium philodendrons
- African violets
- Herbs (multiple)
- Starter shrubs
Price per pot: $0.50-1.50
What is the best estimate for the Volume of a small pot? → 6-inch pots at 1.5-1.8 liters actual capacity
7-INCH NURSERY POT
Specifications:
- Diameter: 7 inches (17.8 cm)
- Height: 6 inches (15.2 cm)
- Total internal Volume: 3.0 liters
- Volume in gallons: 0.79 gallons
- Cubic feet: 0.106 cubic feet
- Cubic inches: 190 cubic inches
Actual Soil Capacity:
- With 1-inch headspace: 2.4 liters
- With 0.75-inch headspace: 2.6 liters
- Practical capacity: 2.4-2.8 liters
- Fill level: 5-5.5 inches from the bottom
Best For:
- Large houseplants
- Medium-sized shrubs
- Tropical plants
- Multiple herb clusters
Price per pot: $0.65-2.00
8-INCH NURSERY POT
Specifications:
- Diameter: 8 inches (20.3 cm)
- Height: 7.5 inches (19 cm)
- Total internal Volume: 4.1 liters
- Volume in gallons: 1.08 gallons
- Cubic feet: 0.145 cubic feet
- Cubic inches: 229 cubic inches
Actual Soil Capacity:
- With 1-inch headspace: 3.5 liters
- With 0.75-inch headspace: 3.7 liters
- Practical capacity: 3.5-3.9 liters
- Fill level: 6.5-7 inches from the bottom
Best For:
- Large houseplants
- Small trees
- Shrubs
- Multi-stem plants
- Floor specimens
Price per pot: $0.75-2.50
Volume of 8-inch pot in liters: 4.1 liters total, 3.5-3.9 liters actual capacity
LARGE POTS (Trees & Shrubs)
10-INCH NURSERY POT
Specifications:
- Diameter: 10 inches (25.4 cm)
- Height: 9 inches (22.9 cm)
- Total internal Volume: 6.5 liters
- Volume in gallons: 1.72 gallons
- Cubic feet: 0.230 cubic feet
- Cubic inches: 366 cubic inches
Actual Soil Capacity:
- With 1-inch headspace: 5.5 liters
- With 0.75-inch headspace: 5.9 liters
- Practical capacity: 5.5-6.2 liters
- Fill level: 8-8.5 inches from the bottom
Best For:
- Tree specimens
- Large shrubs
- Landscape installation
- Specimen plants
Price per pot: $1.00-3.50
12-INCH NURSERY POT
Specifications:
- Diameter: 12 inches (30.5 cm)
- Height: 10 inches (25.4 cm)
- Total internal Volume: 9.2 liters
- Volume in gallons: 2.43 gallons
- Cubic feet: 0.325 cubic feet
- Cubic inches: 519 cubic inches
Actual Soil Capacity:
- With 1-inch headspace: 8.0 liters
- With 0.75-inch headspace: 8.5 liters
- Practical capacity: 8.0-8.8 liters
- Fill level: 9-9.5 inches from the bottom
Best For:
- Mature tree specimens
- Large landscape shrubs
- Premium plants
- Commercial installations
Price per pot: $1.50-5.00
PART 3: 5-GALLON NURSERY POT SPECIFICATIONS
STANDARD 5-GALLON NURSERY POT
Specifications:
Diameter: 10-11 inches (25-28 cm)
Height: 10-11 inches (25-28 cm)
Total internal Volume: 18.9 liters (5.0 gallons)
Volume in cubic feet: 0.667 cubic feet
Volume in cubic inches: 305 cubic inches
Actual Soil Capacity:
- With 1-inch headspace: 15-16 liters
- With 1.5-inch headspace: 14-15 liters
- With 2-inch headspace: 13-14 liters
- Best estimate: 15-18 liters actual capacity
Volume of #5 nursery pot in cubic feet: 0.53-0.64 cubic feet (accounting for headspace)
5-gallon nursery pot actual soil volume cubic feet: 0.53-0.64 cubic feet
5-gallon nursery pot actual soil volume gallons: 15-18 liters = 3.96-4.76 gallons
Why Not Full 5 Gallons?
Headspace Requirement: 1.5-2 inches minimum
- Allows water filling without overflow
- Prevents soil displacement
- Accommodates watering technique
- Reduces soil compaction
Calculation:
- Total 5-gallon pot: 18.9 liters
- Minus 2-inch headspace: ~3.8 liters
- Actual soil capacity: ~15 liters (79% of total)
5 Gallon Pot Applications:
Best For:
- Young trees and shrubs
- Large houseplants
- Landscape nursery stock
- Commercial growing
- Standard transplant size
Price per pot: $1.50-4.00
5 GALLON BUCKET SPECIFICATIONS
Food-Grade Plastic 5 Gallon Bucket:
Specifications:
- Total Volume: 18.9 liters (5 gallons)
- Diameter: 11.2 inches (28.5 cm)
- Height: 13.5 inches (34.3 cm)
- Wall thickness: 0.2 inches (slight taper)
- Cubic feet: 0.667 cubic feet
- Cubic inches: 305 cubic inches
Actual Soil Capacity (for planting):
- With 2-inch headspace: 14-15 liters
- With 3-inch headspace: 12-13 liters
- Best capacity: 14-15 liters for planting
Drainage Considerations:
- Requires drainage holes (drill 4-6 holes)
- Bottom elevation crucial
- Better for short-term than permanent
Price: $2-5 per bucket
PART 4: VOLUME OF POT BY SIZE – QUICK REFERENCE
COMPLETE POT SIZE VOLUME CHART
Pot Diameter × Height → Total Volume → Actual Soil Capacity:
4-inch (10cm):
- 4″ × 4.5″ → 0.65 liters → 0.5-0.6 liters
- Volume in gallons: 0.17 gallons
- Cubic feet: 0.018 cubic feet
5-inch (12.7cm):
- 5″ × 5″ → 1.2 liters → 0.95-1.1 liters
- Volume in gallons: 0.32 gallons
- Cubic feet: 0.042 cubic feet
6-inch (15.2cm):
- 6″ × 5.5″ → 2.0 liters → 1.5-1.8 liters
- Volume in gallons: 0.53 gallons
- Cubic feet: 0.053 cubic feet
Volume of 6-inch nursery pot in liters: 1.5-1.8 liters actual capacity
7-inch (17.8cm):
- 7″ × 6″ → 3.0 liters → 2.4-2.8 liters
- Volume in gallons: 0.79 gallons
- Cubic feet: 0.106 cubic feet
8-inch (20.3cm):
- 8″ × 7.5″ → 4.1 liters → 3.5-3.9 liters
- Volume in gallons: 1.08 gallons
- Cubic feet: 0.145 cubic feet
Volume of 8-inch pot in liters: 3.5-3.9 liters actual capacity
10-inch (25.4cm):
- 10″ × 9″ → 6.5 liters → 5.5-6.2 liters
- Volume in gallons: 1.72 gallons
- Cubic feet: 0.230 cubic feet
12-inch (30.5cm):
- 12″ × 10″ → 9.2 liters → 8.0-8.8 liters
- Volume in gallons: 2.43 gallons
- Cubic feet: 0.325 cubic feet
#5 Nursery Pot (10-11″ × 10-11″):
- Total: 18.9 liters → Actual: 15-18 liters
- Volume in gallons: 5 gallons total → 3.96-4.76 gallons actual
- Cubic feet: 0.667 total → 0.53-0.64 actual
Volume of #5 nursery pot cubic feet: 0.53-0.64 cubic feet
PART 5: SOIL VOLUME PURCHASING CALCULATOR
CALCULATING SOIL NEEDED FOR MULTIPLE POTS
Single Pot Calculation:
Step 1: Determine pot size
- Measure diameter and height
- Look up specifications in the chart above
- Note actual soil capacity
Step 2: Determine quantity needed
- 1 pot → Volume of that pot
- 5 pots → Multiply volume × 5
- 20 pots → Multiply volume × 20
Example: 10 six-inch pots
- Actual soil capacity per pot: 1.5-1.8 liters
- 10 pots × 1.7 liters = 17 liters needed
- Purchase: 20-liter bag (account for settling)
Bulk Pot Calculations:
100 Small (4-inch) Pots:
- Capacity per pot: 0.5-0.6 liters
- Total needed: 50-60 liters
- Purchase: 60-liter or two 30-liter bags
50 Medium (6-inch) Pots:
- Capacity per pot: 1.5-1.8 liters
- Total needed: 75-90 liters
- Purchase: 100-liter or four 25-liter bags
25 Large (8-inch) Pots:
- Capacity per pot: 3.5-3.9 liters
- Total needed: 87.5-97.5 liters
- Purchase: 100-liter or four 25-liter bags
10 #5-Gallon Pots:
- Capacity per pot: 15-18 liters
- Total needed: 150-180 liters
- Purchase: 200-liter or bulk cubic yard
SOIL VOLUME PURCHASING GUIDE
Soil Bag Sizes Available:
Small Bags:
- 2-liter bags: Individual houseplant
- 5-liter bags: 3-4 small pots
- 10-liter bags: 5-6 small to medium pots
Medium Bags:
- 25-liter bags: 12-15 medium pots or 6-8 large pots
- 40-liter bags: 20-25 medium pots or 10-12 large pots
Large Bags:
- 50-liter bags: 25-30 medium pots or 12-15 large pots
- 100 liter bags: 50-60 medium pots or 25-30 large pots
Bulk:
- Cubic yard: 760 liters (27 cubic feet)
- Covers: 400-500 medium pots or 100-150 #5 pots
Soil Settling Factor:
Account for settling:
- Soil compacts over time
- Some water absorption
- Purchase 10-15% more than calculated
- Example: Calculate 50 liters → Purchase 55-60 liters
PART 6: POT VOLUME CONVERSIONS
UNIT CONVERSION REFERENCE
Cubic Inches to Litres:
- Divide cubic inches by 61.024 = litres
- Example: 127 cubic inches ÷ 61.024 = 2.08 liters
Cubic Inches to Gallons:
- Divide cubic inches by 231 = gallons
- Example: 127 cubic inches ÷ 231 = 0.55 gallons
Cubic Feet to Litres:
- Multiply cubic feet by 28.317 = litres
- Example: 0.053 cubic feet × 28.317 = 1.5 liters
Cubic Feet to Gallons:
- Multiply cubic feet by 7.481 = gallons
- Example: 0.053 cubic feet × 7.481 = 0.39 gallons
Litres to Gallons:
- Multiply litres by 0.264 = gallons
- Example: 2.0 liters × 0.264 = 0.53 gallons
Gallons to Litres:
- Multiply gallons by 3.785 = litres
- Example: 5 gallons × 3.785 = 18.9 liters
QUICK REFERENCE CONVERSION TABLE
Common Pot Conversions:
| Pot Size | Litres | Gallons | Cubic Feet | Cubic Inches |
|---|---|---|---|---|
| 4-inch | 0.65 | 0.17 | 0.018 | 40 |
| 6-inch | 2.0 | 0.53 | 0.053 | 127 |
| 8-inch | 4.1 | 1.08 | 0.145 | 229 |
| 10-inch | 6.5 | 1.72 | 0.230 | 366 |
| 12-inch | 9.2 | 2.43 | 0.325 | 519 |
| #5 pot | 18.9 | 5.0 | 0.667 | 1,056 |
PART 7: CALCULATING POT VOLUME WITH FORMULAS
CYLINDRICAL POT FORMULA
Formula: V = π × r² × h
Variables:
- V = Volume (cubic inches initially)
- π = 3.14159
- r = radius (diameter ÷ 2)
- h = height
Step-by-Step Example (8-inch pot):
Step 1: Measure dimensions
- Diameter: 8 inches
- Height: 7.5 inches
- Radius: 8 ÷ 2 = 4 inches
Step 2: Calculate volume
- V = 3.14159 × 4² × 7.5
- V = 3.14159 × 16 × 7.5
- V = 376.99 cubic inches
Step 3: Convert to litres
- Cubic inches ÷ 61.024 = litres
- 376.99 ÷ 61.024 = 6.18 liters total
Step 4: Determine actual capacity
- Subtract headspace (approximately 1.5 inches)
- 6.18 liters × 0.85 = 5.25 liters practical
- More accurate estimate: 3.5-3.9 liters (from chart)
RECTANGULAR POT FORMULA
Formula: V = L × W × H
Variables:
- V = Volume (cubic inches initially)
- L = Length
- W = Width
- H = Height
Example (Window Box: 24″ × 6″ × 6″):
Step 1: Measure dimensions
- Length: 24 inches
- Width: 6 inches
- Height: 6 inches
Step 2: Calculate volume
- V = 24 × 6 × 6
- V = 864 cubic inches
Step 3: Convert to litres
- 864 ÷ 61.024 = 14.16 liters total
Step 4: Determine actual capacity
- With 1-inch headspace: ~12 liters
- Practical capacity: 12-13 liters for soil
PART 8: SOIL VOLUME BY POT TYPE
BEST ESTIMATE FOR VOLUME OF SMALL POT
“Small Pot” Definition:
- Diameter: 4-6 inches
- Height: 4-5.5 inches
- Best estimate: 0.5-2.0 liters
Most Common Small Pot (4-inch):
- Total volume: 0.65 liters
- Actual soil capacity: 0.5 liters (with headspace)
- Best estimate: 0.5 liters for soil purchasing
Most Practical Small Pot (6-inch):
- Total Volume: 2.0 liters
- Actual soil capacity: 1.5-1.8 liters
- Best estimate: 1.5 liters for soil purchasing
What is the best estimate for the Volume of a small pot?
→ 6-inch standard pot at 1.5 liters actual capacity (most common “small pot”)
VOLUME OF POT BY PURPOSE
Seedling/Starter Pots:
- Typical size: 2-4 inch diameter
- Volume: 0.3-0.6 liters
- Best for: New seedlings, small cuttings
Houseplant Pots:
- Typical size: 6-8 inch diameter
- Volume: 1.5-3.9 liters
- Best for: Most indoor plants
Statement/Floor Plants:
- Typical size: 10-12 inch diameter
- Volume: 6.5-9.2 liters
- Best for: Large indoor specimens
Nursery/Commercial Pots:
- Typical size: 1-gallon to 5-gallon
- Volume: 3.8-18.9 liters
- Best for: Wholesale plants, landscape stock
FAQs: Soil Volume For Pots
Q: What is the actual soil volume capacity of a standard 5 gallon nursery pot?
A: A standard 5 gallon nursery pot has a total internal volume of 18.9 liters (5.0 gallons), but the actual soil capacity accounting for necessary headspace is 15-18 liters (3.96-4.76 gallons). The difference accounts for the 1.5-2 inch headspace needed to prevent water overflow during watering and allow proper drainage technique. Most growers use 15-16 liters of soil in a 5 gallon pot to be safe.
Q: Why shouldn’t I fill a 5 gallon pot completely with soil?
A: Headspace is essential for several reasons. It allows water to be applied without overflowing, prevents soil from being displaced during watering, provides space for drainage technique, and reduces soil compaction damage. A 1.5-2 inch headspace is industry standard and leaves room for the plant to be watered properly without soil washing away.
Q: What is the volume of an 8 inch pot in liters?
A: An 8-inch nursery pot has a total internal volume of approximately 4.1 liters (1.08 gallons), but the actual soil capacity accounting for headspace is 3.5-3.9 liters. This makes the 8-inch pot suitable for large houseplants, small trees, shrubs, and multi-stem plants where you need more root space than a 6-inch pot provides.
Q: How much soil do I need for a 6 inch nursery pot?
A: A standard 6-inch nursery pot has a total volume of 2.0 liters but the actual soil capacity is 1.5-1.8 liters when accounting for headspace. This is the most common houseplant pot size and works perfectly for medium-sized plants like philodendrons, pothos, snake plants, and most herbs grown individually. Purchase a 2-liter soil bag to fill one pot comfortably.
Q: What is the best estimate for the volume of a small pot?
A: The best estimate for a “small pot” is a 6-inch diameter pot with an actual soil capacity of 1.5 liters. This is the most commonly used small pot for houseplants and provides good balance between being compact and having adequate root space. If you have a 4-inch pot instead, the estimate is 0.5 liters. Always verify your specific pot dimensions for accuracy.
Q: How do I calculate soil volume for an unusual pot shape?
A: For cylindrical pots, use the formula V = π × r² × h (where r is radius and h is height). For rectangular pots, use V = length × width × height. Calculate volume in cubic inches, then divide by 61.024 to convert to litres. Always subtract 1-2 inches of height for headspace to get actual soil capacity. If the shape is irregular, fill with water to a known level, then measure the water volume.
Q: What is the volume of a #5 nursery pot in cubic feet?
A: A #5 nursery pot (standard 5 gallon pot) has a total volume of 0.667 cubic feet. However, accounting for the necessary 1.5-2 inch headspace, the actual soil capacity is approximately 0.53-0.64 cubic feet. If you’re working with large soil volumes, remember that a cubic yard equals 27 cubic feet or approximately 760 liters, which would fill roughly 40-50 five-gallon pots.
Q: Can I use a 5 gallon bucket as a planter instead of a nursery pot?
A: Yes, you can use a food-grade 5 gallon bucket as a planter, but it requires modification. You must drill drainage holes in the bottom (4-6 holes recommended) to prevent waterlogging and root rot. The actual soil capacity is the same as a 5 gallon pot (15-18 liters), but buckets are taller and narrower, which may affect water drainage patterns. Buckets work better as temporary containers than permanent installations.
Q: How much soil do I need for 10 eight-inch pots?
A: Each 8-inch pot needs approximately 3.5-3.9 liters of soil. For 10 pots: 10 × 3.7 liters = 37 liters. Add 10-15% for settling: 37 × 1.1 = 40.7 liters. Purchase a 50-liter bag or two 25-liter bags. Having extra soil is better than running short, and any unused soil keeps for future plantings.
Q: What’s the difference between total pot volume and actual soil capacity?
A: Total pot volume is the full internal capacity from bottom to rim (100% space). Actual soil capacity is the practical amount of soil you should use, which is 85-95% of the total volume after accounting for 1-2 inch headspace. This headspace is crucial for plant health, drainage, and proper watering technique. Always use actual soil capacity when calculating soil purchases.
Q: How do I convert between litres and cubic feet for soil calculations?
A: Multiply cubic feet by 28.317 to get litres (Example: 0.5 cubic feet × 28.317 = 14.16 liters). To convert litres to cubic feet, divide by 28.317 (Example: 50 liters ÷ 28.317 = 1.77 cubic feet). For soil bag purchases, litres are more intuitive. For large landscape projects, cubic feet or cubic yards are more practical.
Q: Why does soil volume change after potting?
A: Potting soil compacts over time due to watering, plant root growth, and natural settling. Purchase 10-15% more soil than your calculated volume to account for this settling. Some water absorption also occurs as soil moisture equilibrates. After the first heavy watering, you may notice the soil level drops slightly—this is normal and expected.
Q: What’s the most economical way to buy soil for large quantities?
A: For 100+ liters, bulk soil is most economical. A cubic yard (27 cubic feet or 760 liters) costs significantly less per litre than bags and can fill 40-50 five-gallon pots. However, you’ll need storage space and equipment to handle bulk delivery. For smaller projects (under 50 liters), purchasing 25-50 liter bags from garden centers is more practical and cost-effective when accounting for storage.
Q: Can I reuse soil from old pots?
A: Yes, you can reuse potting soil, but refresh it first. Old soil may be compacted, depleted of nutrients, and potentially contain disease pathogens or insect eggs. Remove the top 2-3 inches, then mix the remaining soil 50/50 with fresh soil. Add fresh compost or fertilizer to restore nutrients. Never reuse soil from diseased plants without sterilizing it first (bake at 180°F for 30 minutes).
Q: What type of soil should I use for different pot sizes?
A: Use general-purpose potting mix for most houseplants and standard pots. For small pots (under 6 inches), use seed-starting mix which is lighter and drains faster. For large pots (10+ inches), add orchid bark or perlite to improve drainage and prevent compaction. For succulents, use cactus-specific mix with extra perlite. For orchids and epiphytes, use orchid bark mix. Choose soil type based on plant needs, not pot size.
Q: How accurate do pot volume measurements need to be?
A: For houseplant potting, measurements need only be approximately accurate (within 10-20%). Small variations in volume don’t significantly affect plant health. However, for commercial operations, landscape installations, or very large quantities, accuracy should be within 5%. Always use actual soil capacity (with headspace) rather than total pot volume when purchasing soil, as this has a larger practical impact.
Q: What if my pot doesn’t match standard sizes?
A: Measure the diameter at the widest point and the internal height from bottom to rim. Use the cylindrical formula V = π × r² × h or rectangular formula V = length × width × height to calculate. Remember that radius is half the diameter. Convert cubic inches to litres by dividing by 61.024. Subtract 1-2 inches of height for headspace to get actual soil capacity. When in doubt, use water to verify volume.
Q: Is it better to buy one large bag or multiple smaller bags of soil?
A: One large bag is more economical per litre. However, smaller bags are lighter, easier to carry, easier to store, and useful for adding amendments. For single potting projects, one appropriately-sized bag works best. For ongoing plant care, keeping different bag sizes on hand provides flexibility. Large bags (50+ liters) should be stored in a cool, dry place to prevent compaction and mold growth.
Q: How long does potting soil last before it goes bad?
A: Quality potting soil lasts 1-2 years if stored properly (dry, cool location, sealed bag). Over time, soil loses water retention properties, nutrients deplete, and organic matter breaks down. Once opened, potting soil should be used within 3-6 months before it begins losing quality. For best results, use fresh soil for each potting season. Store opened bags in sealed containers to prevent drying.
Q: Can I mix my own potting soil instead of buying pre-made?
A: Yes, you can make custom potting mix for specific needs. A basic recipe: 40% peat moss or coco coir + 40% perlite + 20% compost. For indoor houseplants: 50% coconut coir + 30% perlite + 20% worm castings. For succulents: 40% potting soil + 30% perlite + 20% orchid bark + 10% sand. For orchids: 100% orchid bark. Homemade mixes are cost-effective for large quantities and allow customization for specific plant needs.
Q: What volume of soil do I need for seed starting?
A: Seed-starting containers are typically much smaller than regular pots. For a standard seed tray (11″ × 21″), use 2-3 liters of seed-starting mix. For a 4-inch seed pot, use 0.25-0.5 liters. Always use lightweight, well-draining seed-starting mix rather than regular potting soil, as seeds need moisture retention but excellent drainage. Seed-starting mix compacts less and provides better aeration for delicate seedlings.
🛒 BEFORE YOU BUY SOIL – CHECKLIST
Measure Your Pots:
- ✅ Measure diameter (at widest point)
- ✅ Measure height (from bottom to rim)
- ✅ Note the total number of pots
- ✅ Identify if standard or unusual shape
- ✅ Take photos for reference
Calculate Volume Needed:
- ✅ Look up pot size in the chart OR calculate with the formula
- ✅ Use actual soil capacity (not total Volume)
- ✅ Multiply by the number of pots
- ✅ Add 10-15% for settling/compaction
- ✅ Select appropriate soil bag size
Choose Soil Type:
- ✅ Potting mix (general purpose)
- ✅ Seed starting mix (seedlings)
- ✅ Orchid mix (orchids/epiphytes) Delivery mix (succulents)
- ✅ Premium blend (high-quality plants)
Account for Logistics:
- ✅ Delivery vs. pickup considerations
- ✅ Storage space for soil bags
- ✅ Bulk discounts if buying a large quantity
- ✅ Soil shelf life (use within season)
- ✅ Budget for soil + other supplies
🗓️ SOIL PURCHASING TIMELINE
PLANNING PHASE (1-2 weeks before):
- Measure all pots
- Calculate the total soil volume needed
- ResearchDeliverytions
- Compare pricing
PURCHASING PHASE (1 week before):
- Order or buy soil
- Arrange dDeliveryif needed
- Gather potting supplies
- Prepare work area
POTTING PHASE (Day of):
- Gather pots and soil
- Set up a potting station
- Fill pots systematically
- Water after potting
- Clean and organize
MAINTENANCE PHASE (Ongoing):
- Monitor soil moisture
- Add drainage amendments if needed
- Replenish the topsoil if it is settling
- Plan next repotting season
RESOURCES
Soil Volume Calculation & Nursery Pot Specifications
- https://www.gardenmyths.com – Comprehensive soil volume calculations and nursery pot specifications guide
Video Pot Volume & Soil Mixing Tutorials
- https://www.youtube.com – Visual guides for calculating pot volumes and soil preparation techniques
Nursery Pot & Container Availability
- https://www.lowes.com – Standard nursery pots, containers, and soil products in the USA
Planter Selection & Soil Volume Planning
- https://www.houzz.com – Design inspiration for pot sizing and soil volume planning
DISCLAIMER
This soil volume calculator guide is educational and provides standard measurements for typical nursery pots. Individual pot dimensions vary by manufacturer – verify measurements for your specific pots. Actual soil capacity depends on headspace preference (typically 1-2 inches) and variations in pot shape. Volume calculations are approximate – use as guidance rather than exact specifications. Soil settling occurs over time – purchase 10-15% more than calculated to account for compaction. Different soil types compact differently – adjust quantities based on soil type. This guide does not replace professional horticultural consultation for specialized growing needs. Measurements assume cylindrical or rectangular standard pots – unusual shapes may vary. Headspace requirements vary by plant type and watering method – adjust accordingly. Metric and imperial conversions are approximate – verify for critical applications.
