๐ผ๏ธ Picture Frame Mat Calculator
Any consistent unit works (e.g. cm) โ just use the same unit for all values.
Enter your artwork's (photo or print) width and height, how much the mat should overlap the edges of the artwork, and the mat's border width, to calculate the mat's window opening size and the outer size needed for framing.
How to use
- Enter the artwork's width and height.
- Enter the overlap โ how much the mat opening should cover the artwork's edges (typically a few mm).
- Enter the mat's border width.
- The mat's opening size and outer size are calculated automatically.
How the calculation works
Work out the window (opening) size of a mat for framing a photo or artwork, and the matโs outer size. Window = artwork size โ 2 ร overlap Outer size = window + 2 ร mat border The overlap is how far the mat covers the edge of the artwork. Making the window slightly smaller than the artwork stops it falling through and hides its edges. As framers do, the border is measured from the edge of the window to the outside of the mat. The outer size is the inside dimension the frame needs.
Worked example
Artwork 20 cm ร 25 cm, overlap 0.3 cm, border 5 cm Window = 19.4 cm ร 24.4 cm Outer = 19.4 + 10 = 29.4 cm, 24.4 + 10 = 34.4 cm โ choose a frame with an inside size of about 29.4 cm ร 34.4 cm A slightly wider bottom border (a weighted mat) also gives a pleasing balance.
Things to be aware of
- Typical overlap: 3โ5 mm for photos, about 5 mm for paintings.
- If the overlap is half the artworkโs width or more, there is no window, so nothing is calculated.
- Ready-made frames come in standard sizes, so you can also pick the border to fit a standard outer size.
FAQ
What is the overlap?
Itโs how much smaller the matโs window opening is than the artwork, so the mat slightly covers the artworkโs edges. This hides the edge of the artwork under the mat for a clean, gap-free look. Enter whatever amount you prefer.
What does the outer size represent?
Itโs the overall size of the mat โ the size your frameโs inner opening needs to be. It equals the window opening plus the border width on all four sides.
What formula is used?
Opening width = artwork width โ 2รoverlap, opening height = artwork height โ 2รoverlap. Outer width = opening width + 2รborder width, outer height = opening height + 2รborder width. As framers do, the border is measured from the edge of the window to the outside of the mat.