Picture Frame Mat Calculator
Work out exactly where to cut a mat. Enter your artwork and frame size (or the border you want) to get the mat opening, every border width, optional bottom weighting and a cut diagram, in inches with fractions or in centimeters.
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Picture or print size
Mat covers the art edge by this much (1/4 in typical). Negative = float gap.
0 = equal borders; 1/4–1 in is classic
How to use the Picture Frame Mat Calculator
- Choose a mode: you already have a frame, or you want a set border width.
- Enter the artwork size and how much the mat should overlap each edge (1/4 in is typical).
- Enter the frame size (the mat's outer size) or the border width you want.
- Add bottom weighting if you want a slightly deeper bottom border, or leave 0.
- Press Calculate and mark the board using the cut diagram measurements.
Mat formulas
- Opening width = artwork width − 2 × overlap; opening height = artwork height − 2 × overlap
- Side borders = (frame width − opening width) ÷ 2
- Top border = (frame height − opening height − bottom weight) ÷ 2
- Bottom border = top border + bottom weight
- Frame size for a chosen border = opening + 2 × border (+ bottom weight on the height)
Worked example: an 8 × 10 in photo, 1/4 in overlap, in an 11 × 14 in frame with 1/2 in bottom weighting. The opening is 7 1/2 × 9 1/2 in. Sides: (11 − 7.5) ÷ 2 = 1 3/4 in. Top: (14 − 9.5 − 0.5) ÷ 2 = 2 in. Bottom: 2 + 0.5 = 2 1/2 in. Check: 2 + 9.5 + 2.5 = 14 in.
Common mat and frame combinations
| Artwork | Opening (1/4″ overlap) | Frame | Sides | Top / bottom (equal) |
|---|---|---|---|---|
| 4 × 6 in | 3 1/2 × 5 1/2 in | 8 × 10 in | 2 1/4 in | 2 1/4 in |
| 5 × 7 in | 4 1/2 × 6 1/2 in | 8 × 10 in | 1 3/4 in | 1 3/4 in |
| 5 × 7 in | 4 1/2 × 6 1/2 in | 11 × 14 in | 3 1/4 in | 3 3/4 in |
| 8 × 10 in | 7 1/2 × 9 1/2 in | 11 × 14 in | 1 3/4 in | 2 1/4 in |
| 8 × 10 in | 7 1/2 × 9 1/2 in | 12 × 16 in | 2 1/4 in | 3 1/4 in |
| 11 × 14 in | 10 1/2 × 13 1/2 in | 16 × 20 in | 2 3/4 in | 3 1/4 in |
| 12 × 18 in | 11 1/2 × 17 1/2 in | 18 × 24 in | 3 1/4 in | 3 1/4 in |
| 16 × 20 in | 15 1/2 × 19 1/2 in | 22 × 28 in | 3 1/4 in | 4 1/4 in |
Tips for cutting a clean mat
- Mark the lines on the back of the board so pencil never shows, and measure each border from the outer edge.
- Cut the outer size first and check it is square: equal diagonals mean square corners.
- Use a sharp blade for every mat; a dull blade tears the core and leaves hooks in the corners.
- Over-cut the corners by a hair less than the board thickness so they release cleanly without visible overcuts.
- For archival framing, choose acid-free or conservation mat board and hinge the art with reversible tape.
Frequently asked questions
How do I calculate the mat opening size?
Subtract twice the overlap from each artwork dimension. For an 8 × 10 in print with a 1/4 in overlap on each side, the opening is 8 − 0.5 = 7 1/2 in wide by 10 − 0.5 = 9 1/2 in tall. The overlap keeps the print from falling through the window.
How do I find the border widths for a given frame?
Side border = (frame width − opening width) ÷ 2. Top border = (frame height − opening height − bottom weight) ÷ 2, and the bottom border is the top plus the bottom weight. A 7 1/2 × 9 1/2 in opening in an 11 × 14 in frame with no weighting gives 1 3/4 in sides and 2 1/4 in top and bottom.
What is a bottom-weighted mat?
A mat whose bottom border is a little wider than the top and sides, often by 1/4 to 1 in. Equal borders can make the picture look like it is sliding down, because our eyes read the optical center of a frame slightly above the true center. Extra weight at the bottom balances it.
How much should a mat overlap the artwork?
About 1/8 to 1/4 in (3–6 mm) on each side is common. Small or fragile pieces can use 1/8 in; larger prints, or art with uneven edges, often use 1/4 in. If you want the whole sheet visible, use a float mount: a negative overlap here leaves a gap and the art is hinged to the backing board.
How wide should mat borders be?
There is no fixed rule, but borders of 2 to 3 1/2 in are typical for frames up to about 16 × 20 in, and wider borders suit small art or large frames. Borders under 1 in tend to look cramped. Many framers also prefer borders that are wider than the frame moulding.
What size mat board sheet do I need?
Standard full sheets are 32 × 40 in, with oversize sheets of 40 × 60 in. The calculator shows how many mats of your outer size can be cut from one 32 × 40 in sheet; leave a little extra for squaring the edges.
Should the mat outer size equal the frame size?
Yes. A frame sold as 11 × 14 in has a rabbet (inside opening) sized to hold an 11 × 14 in mat, glass and backing, usually with about 1/8 in of play. Cut the mat to the nominal frame size, not to the visible window of the moulding.
Are all the tools on FreeToolCabin tested for quality and accuracy?
Yes! Every tool on our site undergoes automated Q/A testing in real browser environments to ensure high precision, correct output, and zero errors. If you happen to spot a bug or have a suggestion, please contact us at [email protected] and our team will review it right away.