How to Choose the Right Mat Size for Frame (Complete Guide)
You found the perfect photo or print, you bought a frame you love, and then you hit a wall: what mat size do you actually need? Suddenly there are window openings, border widths, standard sizes, custom cuts, and you just want your art to look good on the wall. Take a breath. Once you understand a few simple ideas, choosing a mat becomes easy, and you can even let our mat size calculator do the math for you in seconds.
Here is the honest truth most people learn the hard way: the right mat turns ordinary framing into something that looks like it belongs in a gallery, while the wrong mat can make even beautiful artwork feel cramped and awkward. The good news is that getting it right is mostly about proportion, and proportion follows a handful of friendly rules. Let’s walk through all of them.
What Is a Mat, Exactly?
A mat (sometimes called a mat board) is a piece of cardboard, ideally acid-free, with a window cut out of the center. Your artwork sits behind that window so it shows through, while the mat creates a clean border between your art and the frame. That border is not just decoration. It gives your piece room to breathe, and it physically lifts the artwork away from the glass so moisture and condensation can’t ruin it over time.
To talk about mats clearly, you only need three terms:
- Overall size — the full outer dimensions of the mat board, which must match your frame size.
- Window opening — the cutout where your artwork is visible. This is sized to your photo or print.
- Mat border (mat width) — the space between the edge of the window and the outer edge of the board.
Quick example: a 16×20-inch mat with an 11×14-inch window opening gives you a 2.5-inch border on the sides and roughly 3 inches on the bottom, depending on how you center it. Keep those three words in mind and the rest of this guide will click into place.
How to Calculate Your Own Mat Size
If your artwork is an oddball size, you can work out the mat yourself in four steps. This is exactly what a calculator automates, but it’s good to understand the logic.
- Measure your artwork. Note the width and height in inches.
- Pick your borders. Choose a top-and-side width, then make the bottom border about 0.5 to 1.5 inches larger.
- Add it up. Overall width = artwork width + left border + right border. Overall height = artwork height + top border + bottom border.
- Check frame availability. If your result doesn’t match a standard frame, round up to the nearest standard size and spread the extra space into the borders.
Worked example: a 5×7 photo with 2-inch top and side borders and a 3-inch bottom border gives an overall width of 5 + 2 + 2 = 9 inches and a height of 7 + 2 + 3 = 12 inches. Since 9×12 isn’t a common frame, you’d jump up to a standard 11×14 mat and simply widen the borders a touch.
Mat Size Calculator
Enter your photo or print size, choose how wide you want the border, and get the exact mat overall size, window opening, and the nearest standard frame to buy. New to matting? Start with our complete guide to choosing the right mat size for the full walkthrough.
- Window opening5 × 7 in
- Top & side borders2 in
- Bottom border3 in
How to use this mat size calculator
Type in the width and height of your photo or print, then pick a border style. The tool adds your chosen borders around the artwork to give you the overall mat size, keeps the window opening matched to your art, and suggests the closest standard frame so you don't have to pay for a custom cut. Switch between inches and centimeters anytime.
Why bottom borders are bigger
Notice the bottom border is wider than the top and sides. That's the rule of thirds framers use: a perfectly even border looks bottom-heavy to the human eye, so adding a little extra weight at the bottom makes the finished piece look balanced and intentional.
Quick standard frame reference
| Artwork | Suggested mat | Frame |
|---|---|---|
| 4 × 6 photo | 4 × 6 window | 8 × 10 |
| 5 × 7 photo | 5 × 7 window | 8 × 10 or 11 × 14 |
| 8 × 10 photo | 8 × 10 window | 11 × 14 or 16 × 20 |
| 11 × 14 print | 11 × 14 window | 16 × 20 |
| 18 × 24 poster | 18 × 24 window | 22 × 28 |
Frequently asked questions
What size mat do I need for a 5x7 photo?
How wide should the bottom mat border be?
Do I round up to a standard frame size?
What is a double mat?
Should I use acid-free mat board?
Standard Mat Sizes (What Stores Actually Stock)
Most framers and craft stores keep a predictable set of standard mat sizes on the shelf. Buying one of these is cheaper and faster than ordering custom, so it’s worth knowing them before you shop.
Small mats
- 5×7 inches, usually with a 3×5 window
- 8×10 inches, usually with a 5×7 window
Medium mats
- 11×14 inches, with an 8×10 window
- 16×20 inches, with an 11×14 window
- 18×24 inches, with a 13×19 window
Large mats
- 20×24 inches, with a 16×20 window
- 22×28 inches, with an 18×24 window
- 24×36 inches, with a 20×32 window
If your art doesn’t match any of these, don’t worry. You can either round up to the next standard size and adjust the borders, or order a custom mat cut to your exact dimensions. We’ll cover both.
The One Rule That Makes Mats Look Professional
Here’s the secret framers rarely explain out loud: it’s all about proportion. The most reliable trick is the rule of thirds, where the bottom border is slightly larger than the top and sides. Your eye reads a perfectly even border as bottom-heavy because of how we perceive space, so framers add a little extra at the bottom to make everything look balanced.
A classic combination looks like this:
- Top and sides: 2 inches each
- Bottom: 3 inches
That tiny adjustment is the difference between “nicely framed” and “why does this look slightly off?” Beyond that, you mostly choose how generous you want the border to feel:
Gallery (minimal)
About 1 inch on top and sides, 1.5 inches on the bottom. Clean, modern, and great for larger pieces where you don’t want the mat to overpower the art.
Classic (standard)
Around 2 inches top and sides, 3 inches on the bottom. This is the safe, traditional choice that flatters almost any artwork.
Museum (generous)
Roughly 3 inches top and sides, 4 to 5 inches on the bottom. Wide borders make small or precious pieces feel important, like they’re worth pausing in front of. The bigger the border, the more upscale the piece tends to read.
Photo Mat Sizes for Common Print Dimensions
Most family photos come in a few predictable sizes, so here are the easy pairings that just work.
- 4×6 photo → 8×10 mat with a 4×6 window. Even 2-inch borders, fits a standard 8×10 frame.
- 5×7 photo → 8×10 mat (tighter, modern) or 11×14 mat (roomier, elegant). The 11×14 gives a generous 3-inch border that feels gallery-grade.
- 8×10 photo → 11×14 mat for a snug, clean look, or 16×20 mat with wide 4-inch borders for real presence.
- 11×14 photo → 16×20 mat (2.5-inch sides) or 20×24 mat for a more dramatic, spacious frame.
- 16×20 photo → 20×24 mat with even 2-inch borders all around.
Print and Poster Mat Sizes
Art prints and posters often come in less tidy dimensions, so a little planning helps.
- 5×11 print (letter size) → 11×14 mat, about 1.25-inch sides and 1.75-inch bottom. Fits a common 11×14 frame.
- 11×17 print (tabloid) → 16×20 mat, roughly 2.5-inch sides with a slimmer bottom.
- 12×18 print → 16×20 mat for a tighter look, or 18×24 mat for balanced 3-inch borders.
- 18×24 poster → 22×28 mat with generous borders for a finished, museum feel.
- 24×36 poster → 28×40 mat with about 2-inch borders, or larger for a more dramatic frame.
Single, Double, or Triple Matting?
A single mat is the everyday choice and looks great on its own. But if you want to add a quiet touch of luxury, double matting is the move. A double mat layers two boards so a thin sliver of the inner mat color, usually 1/4 to 1/2 inch, peeks out around your artwork like an accent line.
A favorite combination is a white outer mat with a navy, burgundy, or deep accent inner mat. It frames the art twice and instantly reads as gallery work. To size a double mat, make the outer mat’s window about 1/4 inch larger than the inner mat’s overall size, and the inner mat’s window about 1/4 inch larger than the artwork. Triple matting adds a third layer for a true museum effect, though it’s usually saved for valuable pieces because the cost climbs quickly.
Mat Board: Materials, Colors, and Finishes
Material
Choose acid-free mat board (often called museum or conservation board) for anything you want to keep. Regular board contains acid that slowly yellows and damages art, so it’s only fine for temporary or low-value displays. For photos and prints with sentimental or monetary value, acid-free is non-negotiable.
Color
Neutrals are the safest and most versatile: white reads clean and classic, cream feels warm and traditional, and light gray leans contemporary. Statement colors like navy, burgundy, forest green, charcoal, and black can be gorgeous, but let the artwork lead. As a rule, the mat should support the art, not compete with it.
Finish
A matte finish is the standard for good reason: it’s non-reflective and never steals attention from your piece. Linen-textured mats add subtle elegance at a higher price, while glossy finishes are generally avoided because the shine fights the artwork.
Where to Buy Mats (and the DIY Option)
- Craft and art stores (such as Michaels or Blick) stock standard pre-cut mats for roughly $5–$15 and can order custom sizes.
- Online retailers are often cheaper for standard sizes, sometimes $3–$10, with in-store pickup options.
- Professional framing shops cut to exact specifications using acid-free materials and give expert advice, at a higher price point.
- DIY cutting is doable with a mat cutter ($20–$50), mat board, and a straightedge, but it takes practice to get clean, accurate bevels.
As a rough budget guide, expect $15–$30 for a standard custom mat, $30–$50 for a custom double mat, and $50 or more for elaborate triple mats.
Quick Mat Size Reference Chart
Bookmark this table. It covers the pairings you’ll reach for most often.
Artwork size | Recommended mat | Window opening | Typical borders |
4×6 photo | 8×10 | 4×6 | 2″ all sides |
5×7 photo | 8×10 or 11×14 | 5×7 | 1.5″–2″ top/sides, 2″–3″ bottom |
8×10 photo | 11×14 or 16×20 | 8×10 | 1.5″–2″ top/sides, 2″–3″ bottom |
11×14 photo | 16×20 or 20×24 | 11×14 | 2.5″ top/sides, 3″ bottom |
8.5×11 print | 11×14 | 8.5×11 | 1.25″ top/sides, 1.75″ bottom |
11×17 print | 16×20 | 11×17 | 2.5″ top/sides, 1.5″ bottom |
16×20 photo | 20×24 | 16×20 | 2″ all sides |
18×24 poster | 22×28 or 24×36 | 18×24 | 2″–3″ all sides |
24×36 poster | 28×40 | 24×36 | 2″–3″ all sides |
Pro Tips for Mats That Look Expensive
- Keep it simple. One clean mat color, usually white or cream, beats a busy multi-color stack almost every time.
- Match the mood to the art. White or gray for modern and abstract work, cream or muted earth tones for landscapes, soft neutrals for portraits.
- Protect the air gap. The mat keeps your artwork off the glass, which prevents moisture damage. Never skip it for valuable pieces.
- Go acid-free for keepsakes. It’s a small upcharge that protects your photos for decades.
- Stay consistent for gallery walls. Same mat color and border style across several frames creates a calm, cohesive grouping.
FAQs: Mat Size For Frame
What is the ideal bottom border width for a mat?
The bottom border should be about 0.5 to 1.5 inches larger than the top and side borders. A 2-inch top with a 3-inch bottom is the classic, can’t-go-wrong proportion.
Should the mat color match the frame color?
Not necessarily. A white or cream mat with a wood frame is timeless, but the mat color should be chosen to complement the artwork first, not the frame.
Do I even need a mat, or can I frame without one?
Mats are optional but recommended. They create an air gap that protects the art from the glass, add a professional finish, and give the piece visual breathing room. You can skip a mat for casual posters, but valuable art benefits from one.
How much of my artwork should the mat cover?
Ideally none of it. The window opening should reveal your full artwork. The only exception is when you intentionally overlap the edges slightly to hold the piece in place, which framers do carefully.
What standard mat size fits a 24×36 poster?
A 24×36 poster typically uses a 28×40 mat with 2-inch borders all around, or a 30×42 mat if you want a more generous 3-inch border.
Can I double-mat inexpensive artwork?
Absolutely. Double matting elevates the look regardless of the art’s value, so it’s a great way to make an affordable print feel gallery-worthy.
Do larger mats require larger frames?
Yes. The mat’s overall size determines the frame size, so always calculate the mat first and then buy a frame to match.
The Bottom Line
Choosing the right mat comes down to three things: an overall size that matches your frame, a window opening that fits your artwork, and border proportions that follow the rule of thirds. Add acid-free board for anything you want to keep, pick a color that flatters your piece, and you’ve basically done what a professional framer does. Whether you grab a standard pre-cut mat or order a custom cut, those few minutes of planning will make your artwork look like it truly belongs on the wall.
Trusted Sources
For deeper, authoritative guidance on preserving and framing your art, the Library of Congress Preservation Guidelines for Matting and Framing cover museum-quality, acid-free techniques, while the Professional Picture Framers Association (PPFA) sets the professional standards framers follow worldwide.
