A steel rule and pencil laid across a sheet of mat board, marked out for a cut

Size, Mats & Proportion · Tools

Frame & mat size calculator

Enter the size of your artwork and get every dimension you need to order or cut a frame, with a preview drawn to the real proportions. Free, and nothing is sent anywhere.

Units
Artwork size

Width

Height

Measure the whole piece, including any unpainted margin, not just the image area.

Set to 0 for no mat. A border wider than the frame moulding almost always looks better than a narrow one.

The eye reads the centre of a frame as slightly high, so an evenly cut mat looks like it is sagging.

How far the mat covers the edge of the work on each side. Without this the window would be the same size as the piece and nothing would hold it.

Clearance cut into the frame beyond the mat so the package drops in rather than being forced. 2 to 3 mm is normal.

How wide the frame itself is, seen from the front. Used for the outside size and the preview only.

Drawn to scale

Mat board

Cut the mat board to
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Window opening
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Border: top / sides
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Border: bottom
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Frame

Frame size to order
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Outside dimensions
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Moulding length needed
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Glazing & backing

Glass or acrylic, cut to
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Backing board, cut to
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Reading the result

What each number is for

The two that matter most are the window opening and the frame size. The window is deliberately smaller than the artwork, because the mat has to overlap the edge to hold the piece in place. The frame size is deliberately larger than the mat, because the package has to drop into the rebate rather than be forced into it. Get either the wrong way round and the job has to be cut again.

5050 Equal borders Measures right. Looks like it is sliding down. 5060 Weighted bottom Measures uneven. Looks centred.
Left: equal borders on all four sides. Right: the same mat with the bottom border cut about 20 percent deeper. The eye reads the centre of a frame as slightly above the true centre, so an evenly cut mat looks bottom-heavy and the work appears to sag. Weighting the bottom corrects it.

The moulding length is the total run you need, including the mitre waste at the four corners. Buy a little more than that. Off-cuts are cheap; running short on the fourth corner means a fresh length.

If any of this is for a piece you actually own, you are welcome to skip it entirely and send us the measurements. We frame original work in-house and we will do the arithmetic for you.

How to measure your painting Mat border width guide

Common questions

Calculator questions

Why is the window opening smaller than my artwork?

Because the mat has to hold the piece. If the window were exactly the size of the artwork the work would fall through it. The overlap, usually 5 mm on each side, is what sits over the edge and keeps it in place. On a piece with a deckled edge or a visible signature in the margin you may want a float mount instead, which shows the whole sheet.

Why is the frame bigger than the mat?

The rebate is the groove inside the frame that everything sits in, and it needs a little clearance. Cut a frame to exactly the mat size and the package has to be forced in, which bows the mat and can crack the glass. Two to three millimetres is enough.

Should the bottom border really be deeper?

Yes, and it is not a superstition. The eye reads the centre of a rectangle as slightly above the true centre, so a mat with four equal borders looks bottom-heavy and the picture seems to be sliding down. Adding roughly 20 percent to the bottom corrects it. Measured, it is uneven. Looked at, it is centred.

Does this work for a canvas?

Only partly. A stretched canvas usually needs no mat and no glazing, so the mat and glass figures do not apply. What you want there is a floater frame, which is sized from the canvas plus a deliberate gap. See floater frames for canvas.

Are the inch measurements exact?

They are rounded to the nearest sixteenth of an inch, which is the precision framing is actually cut to. If you need it finer than that, work in millimetres.

Or let us do it

We will measure, cut, and fit it for you

Send the piece or send the measurements. Framing done in-house at our gallery on Davie Street in Vancouver.

Ask about framing More sizing guides