Mat board calculator

A mat board calculator is the most searched framing tool for a reason. The mat is the first thing a viewer reads after the artwork. Too tight and the print feels trapped. Too wide and a small photograph looks like it is floating in a field of paper. This calculator treats the mat as geometry, not taste: outer board, window, overlap, and an optional heavier bottom.

The outer size is artwork plus left/right and top/bottom borders. The window is artwork minus overlap on each side. If you cut the window the same as the print, the print can slip and show a hairline gap. A 1/4" overlap is the usual shop default; 1/8" is common on small work where you cannot afford to lose image. The numbers here match what a handheld mat cutter or a Logan-style board will need, without pretending to drive a CNC.

Bottom weighting is built in because equal borders often look wrong on portraits. Set mat width to 2.5" and bottom to 3" and you will see the extra 1/2" appear only on the bottom. In Framing Studio you can drag that edge until the snap hint says Bottom weighted. The calculator is for people who arrived from search and just need the cut size before lunch.

Board size must also match glass and backing. If the mat is 18×24, the acrylic and foamboard should be 18×24, not 18×24 plus a hopeful sliver. Shops waste money when those three parts diverge. This page reports the package size explicitly so you can order glazing from the same numbers you use to mark the mat.

Double-weight vs 4-ply vs 8-ply does not change the window math, but it changes the stack depth later. 8-ply mats eat rabbet space. If you already know you want a thick museum board, open the studio’s stack inspector after you leave this calculator. The fit check will tell you whether a 10 mm rabbet still has remaining depth after glass, two boards, the print, and backing.

Color is design, not arithmetic, but it belongs in the same sitting. A warm ivory mat next to walnut moulding is a different object from a cool white mat next to black. The studio lets you pick colors on the canvas; this calculator stays focused on size so the search result stays honest. Use the Open in Framing Studio button when you want to see the object, not just the tape-measure answer.

Standard frame sizes should influence mat decisions. If you want to drop the finished package into a ready-made 16×20, work backwards: artwork + borders ≈ 16×20. This calculator goes forwards from artwork, which is how most DIY jobs start. The studio will warn you when you are close to a standard and offer a snap. That is faster than hunting a chart.

Photographers printing full-bleed images sometimes skip a mat. That is a valid path — choose no mat in the studio — but this page assumes you came here because you want a board. Posters with a designed white border can still take a mat; just measure the image area you want shown, not the paper.

Keep notes in inches if that is how your cutter’s ruler is printed. Switch to millimetres if you are marking with a metric square. Do not mix a 63.5 mm border with a 2.5" note on the same offcut; the engine can convert, people cannot in a hurry.

When the result looks right, take it into the workshop. The studio draws the window on a board diagram, lists top/bottom/left/right, and later packs moulding. A mat calculator that dead-ends at a table is a toy. This one is a doorway into a build plan.