Calculator + chartEnter your measurements below and it works the answer out.
A mat is what makes a print look framed rather than stuck to a wall. Enter the print and the frame and this gives you the opening to cut and the border on every side.
| Frame size | Pre-cut mat opening | Print it holds | Border |
|---|---|---|---|
| 5 × 7 | 3.5 × 5 in | 4 × 6 | 0.75 in |
| 8 × 10 | 4.5 × 6.5 in | 5 × 7 | 1.75 in |
| 11 × 14 | 7.5 × 9.5 in | 8 × 10 | 1.75 in / 2.25 in |
| 12 × 16 | 8.5 × 11.5 in | 9 × 12 | 1.75 in / 2.25 in |
| 16 × 20 | 10.5 × 13.5 in | 11 × 14 | 2.75 in / 3.25 in |
| 18 × 24 | 11.5 × 17.5 in | 12 × 18 | 3.25 in |
| 20 × 24 | 15.5 × 19.5 in | 16 × 20 | 2.25 in |
| 24 × 36 | 19.5 × 29.5 in | 20 × 30 | 2.25 in / 3.25 in |
Openings assume the standard 1/4 in of mat lapping over each edge of the print, so the opening is half an inch smaller than the print in both directions. Where two border figures are given, the first is the sides and the second the top and bottom.
The opening is smaller than the print. The mat has to lap over the edge of the artwork or the print falls through the hole. A quarter of an inch on each side is the trade standard, which makes the opening half an inch narrower and half an inch shorter than the print itself. An 8 × 10 print takes a 7.5 × 9.5 opening.
The mat outer size is the frame size. Ready-made frames in the US are named for the size of glass and mat they hold, not their outside dimensions. A 16 × 20 frame takes a 16 × 20 mat, and the moulding sits outside that.
The border is what is left over, shared out. Subtract the opening from the frame and split the remainder: half to each side horizontally, and vertically either evenly or with a weighted bottom.
Why the bottom is wider. A picture with even borders reads as sitting low in its frame, because the eye places the optical center above the true center. Framers correct it by giving the bottom border roughly a fifth more than the top. This calculator uses 55 per cent of the vertical border at the bottom and 45 per cent at the top.
When it says go bigger. Below about an inch and a half the mat stops doing its job, and the print looks squeezed rather than presented. If the narrowest border falls under that, the calculator says so and names the smallest standard frame that gives a comfortable border.
A 7.5 × 9.5 inch opening, because the mat laps a quarter inch over each edge. Put that in an 11 × 14 frame and you get about 1.75 inches at the sides and 2.25 inches top and bottom, which is the most common framing combination sold.
A 16 × 20 frame is the standard pairing. It gives a 10.5 × 13.5 inch opening with roughly 2.75 inches at the sides and 3.25 inches top and bottom — generous enough that the print reads as artwork.
Yes, by convention. The eye reads the optical center as slightly above the true center, so a picture with even borders looks like it is sinking. Framers give the bottom about a fifth more than the top to correct it. On a small frame that is a matter of a quarter inch; on a large one it is visible.
A quarter of an inch on each edge is standard. An eighth is the minimum and only works on a print with a clean, straight edge. Go to three eighths or a half inch if the print curls, has a rough deckle edge, or you want to hide a trimmed margin.
The mat has to match the frame, not the print. Ready-made frames are named for the mat and glass they take, so buy the frame first, then a mat cut to that outer size with an opening sized to your print.
Not always, but it does two jobs beyond looks: it holds the artwork off the glass so condensation cannot stick the two together, and it gives the eye a rest between the picture and the moulding. Photographs printed to the full frame size are often hung without one; anything on paper you care about is better with one.
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