Frame Mat Size Calculator

Work out frame mat size instantly with clear inputs, formula shown and shareable results.

About Frame Mat Size Calculator

The mat window is cut slightly smaller than the artwork so the edges are held rather than floating, then the frame opening is the window plus the border on all four sides. A 5-8 cm border suits most artwork, and many framers make the bottom border slightly deeper for visual balance.

Formula

Frame sizing

mat window = artwork - 2 x overlap; frame opening = window + 2 x border

Worked example

With the default values below, Frame Mat Size Calculator returns Frame opening width of 41.00. Change any input above and every figure here is recalculated in your browser.

Inputs used

Artwork width: 30 cm
Artwork height: 40 cm
Mat border: 6 cm
Mat overlap onto the artwork: 0.5 cm

Results

Frame opening width: 41.00 cm
Frame opening height: 51.00 cm
Mat window width: 29.00 cm
Mat board area: 2,091.00 cm²

Step by step

1Values used
2Frame sizing
3Frame opening width= 41.00 cm
4Frame opening height= 51.00 cm
5Mat window width= 29.00 cm
6Mat board area= 2,091.00 cm²

Assumptions and limits

The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

Why overlap the artwork?

So the mat holds the edges down and hides any irregular trim. 3-5 mm on each side is standard.

Why is the bottom border sometimes deeper?

Optical weighting: an equal border looks bottom-light when hung at eye level, so adding 10-20% to the bottom looks more balanced.