How Wide Should a Photo Mat Be?

The mat is the only part of a framed photograph that does nothing. It holds no image, carries no information, and adds cost — and take it away and the picture reads as a snapshot pinned to a wall. That empty margin is a pause. It tells the eye where to stop looking at the room and start looking at the photograph, and how much of a pause you give it is the single decision that separates a framed print from a framed print that looks framed.

There is a number behind the pause, and it is smaller than most people guess. This guide is that number, the arithmetic that follows from it, and what to do when the print you have and the frame you bought disagree.

The rule: 8–12% of the longest side

Measure the longest side of the print. Take 8–12% of it. That is your mat width, and you use the same width on all four sides.

Working from the longest side rather than from each side separately is what keeps a set consistent: a landscape print and a portrait print of the same size end up with the same visual margin, so a wall of them reads as one hang rather than six decisions.

mat width	what it reads as	use it for
5–8%	a border, not a mat	scrapbook elements and journal pages, where the photo should dominate
8–12%	the portrait and gallery convention	anything you intend to frame and hang
12–25%	editorial, magazine breathing room	one strong image that deserves the room

Our own photo mat tool opens at 12%, the top of the gallery band, because that width most reliably reads as deliberate on a first look. Below 8% the board stops behaving like a mat and starts behaving like a coloured edge.

What that is in inches and centimetres

Outer size below is the print plus a margin on each side — before the bottom is weighted, which is the next section.

print	longest side	mat at 8%	at 10%	at 12%	outer size at 10%
4 × 6 in	6 in	0.48 in	0.60 in	0.72 in	5.2 × 7.2 in
5 × 7 in	7 in	0.56 in	0.70 in	0.84 in	6.4 × 8.4 in
8 × 10 in	10 in	0.80 in	1.00 in	1.20 in	10 × 12 in
11 × 14 in	14 in	1.12 in	1.40 in	1.68 in	13.8 × 16.8 in
10 × 15 cm	15 cm	1.2 cm	1.5 cm	1.8 cm	13 × 18 cm
13 × 18 cm	18 cm	1.44 cm	1.80 cm	2.16 cm	16.6 × 21.6 cm

Two of those rows are worth noticing. An 8 × 10 print at 10% lands on a 10 × 12 board, and a 10 × 15 cm print at 10% lands on exactly 13 × 18 cm — the next print size up in both systems. That is not a coincidence so much as a hint: the sizes people already frame are roughly a mat apart from each other.

Fitting a print into a frame you already own

Most people are not cutting a mat to taste. They have a frame, they have a print, and the question is whether the pairing works. Then the arithmetic runs backwards:

margin per side = (frame side − print side) ÷ 2

frame	print	side margin	top & bottom	as % of print’s longest side	verdict
5 × 7 in	4 × 6 in	0.5 in	0.5 in	8%	just inside the gallery band — tight but correct
8 × 10 in	5 × 7 in	1.5 in	1.5 in	21%	the classic pairing, and it lands in editorial territory
8 × 10 in	4 × 6 in	2.0 in	2.0 in	33%	generous; the print starts to look small
11 × 14 in	8 × 10 in	1.5 in	2.0 in	15%	a touch over gallery, reads well
11 × 14 in	5 × 7 in	3.0 in	3.5 in	43%	the print reads as a stamp — print bigger
16 × 20 in	11 × 14 in	2.5 in	3.0 in	18%	editorial, and the reason this pairing is everywhere

Notice that the side and the top margins are not always equal — an 8 × 10 print in an 11 × 14 frame gives 1.5 in at the sides and 2.0 in top and bottom, because the two aspect ratios differ. That is normal and it looks fine. What matters far more than side-versus-top is bottom-versus-top, which is the next section.

Two caveats if you are cutting real board rather than pixels. The table assumes the mat is cut to the frame’s full size. And the window is always cut slightly smaller than the print on every side, so the print cannot drop through it — the exact overlap is a shop convention, so take it from whoever supplies your board rather than from us.

Why the bottom is deeper than the top

With four equal margins, a picture reads as though it is sliding out of the frame — that much you can see for yourself by cutting one. The usual explanation is that the eye places a rectangle’s optical centre slightly above its geometric one, so an evenly cut mat looks bottom-light; whatever the mechanism, framers have corrected for it for a century by weighting — adding to the bottom margin only.

We add about 30%. On an 8 × 10 print at 12%, that means a 1.2 in mat on three sides and 1.56 in at the bottom, for a finished board of 10.4 × 12.76 in. It should not be obvious. If someone can see that the bottom is deeper, you have overdone it.

Weighting is on by default in the tool and there is a switch to turn it off, which is the right call for a photo you are gluing into a spread rather than hanging — on a journal page the mat is a design element, not a frame, and the illusion it corrects doesn’t apply.

The second board, and how much of it to show

A double mat is two boards stacked, the lower one cut slightly larger, so a thin line of a second colour appears just inside the window. It does one job: it separates the photograph from the board so the two don’t bleed into each other, which matters most when the photo has a lot of white or a lot of sky.

The reveal is thin by definition. Ours is drawn at 14% of the mat width — on a 1.2 in mat that is about 0.17 in, on a 0.7 in mat about 0.1 in. Anything much wider stops reading as a line and starts reading as a stripe, and you have made a frame inside a frame.

For the colour: pull it out of the photograph rather than off a swatch card. Run the image through the colour palette tool, take a muted tone that already appears somewhere in the image, and use that as the inner board. A colour the photo already contains will always look considered; a colour it doesn’t will always look chosen.

The one detail that does most of the work on a real mat is the bevel — the 45° cut through the board that exposes its white core as a bright hairline around the picture. It is the difference between a cut mat and a coloured rectangle, which is why we draw it rather than fake it, scaled at 0.8% of the photo’s short side so it stays a hairline at any output size.

When it goes wrong

The picture looks like it is sliding out of the frame. The bottom margin is too shallow. Turn weighting on, or add roughly 30% to the bottom by hand.

It reads as a border, not a mat. You are under 8%. This is the most common miss by a distance, because a mat always looks wider on screen than it does on a wall.

The photo looks like a postage stamp. You are well past 25% for that print size. Print larger, or use a smaller frame — do not split the difference by shaving the mat, because a slightly-too-small print in a slightly-too-thin mat looks like a mistake, whereas either extreme looks like a decision.

The print doesn’t fit the frame you bought. This is an aspect-ratio problem, not a mat problem. Most phone photos come out 4:3, and none of the common frame sizes is 4:3 — 4 × 6 is 3:2, 5 × 7 is 1.4:1, 8 × 10 is 1.25:1. You either crop into the photo or letterbox it inside the window. Crop or letterbox to the frame’s aspect first, then mat the result; doing it in that order means you choose what gets lost instead of discovering it after the print arrives.

The mat is louder than the photograph. Real board is off-white, cream, or a small set of neutrals. Colour belongs in the reveal, where there is a tenth of an inch of it, not in the field, where there are two inches.

Frequently asked questions

How wide should a photo mat be?

Eight to twelve per cent of the print’s longest side, applied on all four sides. On a 5 × 7 print that is 0.56–0.84 in; on an 8 × 10 it is 0.8–1.2 in. Under 8% reads as a border rather than a mat; up to 25% is legitimate for a magazine-style presentation of a single strong image.

What size mat do I need for a 5 × 7 print in an 8 × 10 frame?

A 1.5 in margin on all four sides, from (8 − 5) ÷ 2 and (10 − 7) ÷ 2. That is about 21% of the print’s longest side, which sits above the gallery band and in editorial territory — part of why this particular pairing has been standard for so long.

Why is the bottom of a mat wider than the top?

Because four equal margins make a picture look like it is sliding downward — the conventional explanation is that the eye reads a rectangle’s optical centre as sitting above its geometric centre. Framers add to the bottom to compensate. Around 30% extra is the usual correction, and it should not be visible as an asymmetry.

How wide should the reveal on a double mat be?

Thin. Ours is 14% of the mat width — roughly 0.17 in under a 1.2 in mat. The reveal exists to separate the photograph from the board, not to add a second frame, so if you can measure it by eye it is too wide.

Does a small print need a mat at all?

Not always. Below about 5% the board is a border, and for a photo being glued into a scrapbook or a journal that is often exactly right — the page is already doing the framing. Mats earn their keep when the picture has to hold a wall on its own.

Then go and make something with it

Mat widths are most useful in multiples. A set of prints matted at the same percentage, in the same board colour, hung as a grid, reads as a curated wall rather than an accumulation — the arithmetic above is what makes a set hold together rather than look accumulated. A minimalist family set is the easiest place to try it, because the restraint is already the point.

One case where the percentages want a second look: a print that already carries its own white border. An instant print is the obvious one — a Polaroid is 88 × 107 mm with a 23.5 mm chin built in, so a generous mat around it gives you two frames arguing with each other. Mat those narrow, or mat a set of them together as one piece.

When the widths are settled, cut the mat around your photo in the browser — the photo stays at full resolution and the board is added around it, so nothing is cropped and nothing uploads. Still deciding what the finished piece should feel like? How to choose a collage style is the shorter conversation to have first, and the recipe library is where the finished versions live.