FramingLab

Mat board calculator

Calculate a rectangular mat window and outer board from your photo size and desired artwork borders. Know the image width and height, plus top/side and bottom borders. Board size is also the planned glass and backing size.

Result

Package / glass 16" × 19 1/2"

Mat window 10 1/2" × 13 1/2"

Finished outside 18 5/8" × 22 1/8"

Sight opening 15 5/8" × 19 1/8"

Open in Framing Studio

Your dimensions will carry over. Add your own artwork next.

Board 16" × 19 1/2"Window10 1/2" × 13 1/2"
  • Artwork11" × 14"
  • Window10 1/2" × 13 1/2"
  • Window border · top2 3/4"
  • Window border · bottom3 1/4"
  • Bottom weighting1/2"

Worked example

Board 16" × 19 1/2"Window10 1/2" × 13 1/2"
  • Artwork11" × 14"
  • Window10 1/2" × 13 1/2"
  • Window border · top2 3/4"
  • Window border · bottom3 1/4"
  • Bottom weighting1/2"

Inputs

  • Artwork: 11" × 14".
  • Artwork borders: top and sides 2 1/2"; bottom 3". Overlap: 1/4" on each edge.

Calculated result

Board / glass / backing
16" × 19 1/2"
Mat window
10 1/2" × 13 1/2"
Window borders, before the frame covers them
Top 2 3/4", bottom 3 1/4", left 2 3/4", right 2 3/4"

Use the board result to plan the glass and backing; use the window and window-border measurements to mark the mat. Check the actual frame recess before ordering.

Continue this example in Studio

Calculated with the same FramePlan engine as the tool. Inches display to the nearest 1/16; internal dimensions use 0.01 mm precision. Examples are plans, not measurements of a purchased frame.

Which dimension are you measuring?

Artwork size
The physical photo, print or artwork area used by the calculation. Decide which edges can be covered; do not mix image size with a larger sheet of paper.
Mat window
The opening cut through the matboard. For an overlapped rectangular image, each dimension is artwork size minus twice the overlap.
Board / glass / backing size
The outer size of the rectangular package placed in the frame. Mat borders grow this size; window overlap does not.
Nominal frame size and actual rabbet
A shop’s label usually describes the components it accommodates, not the outside. The actual back recess may include additional fitting room. Check the maker’s sizing convention and measure it before ordering parts.
Sight opening
The opening visible from the front of the frame. The rabbet lip covers the package edges, so this is smaller than the actual rabbet recess.
Finished outside size
The frame measured between its outermost edges. Use it for wall space and long-point rail lengths; do not use it as a retail opening size.

Scope and making notes

This tool starts with a rectangular photo or artwork and your chosen borders, then works outward to a board size. It does not reverse-calculate borders from an existing frame. It uses a single mat and 1/4 inch overlap per artwork edge; change overlap or individual borders in Studio. Double mats have a separate tool.

An input border runs from the artwork edge to the outside board edge. The window border is that input plus overlap. The frame’s lip can hide part of the board; the visible border after assembly depends on the sight opening.

Overlap is a choice, not one universal size. Frame Destination’s mat-opening specifications distinguish artwork size from cut-window size and use different overlap allowances. Protect image details and signatures when choosing yours.

Mat Border Calculator for an Existing Frame

How it works

Outer board width is artwork width plus the left and right borders. Height adds the top and bottom borders.

The window is smaller than the artwork by the overlap on each side, so the print cannot slip and flash a white edge.

Bottom weighting adds extra mat only at the bottom. The other three sides stay at the mat width you typed.

Common mistakes

Frequently asked questions

How do I calculate mat board size?

Add the side borders to the artwork width, and the top and bottom borders to the height.

What overlap should I use?

This tool uses 1/4 inch per side as an example allowance. Overlap depends on the image and supplier; check important details and change it in Studio if needed.

What is bottom weighting?

A slightly taller bottom border so the artwork does not look low in the frame.

Does this cut oval windows?

Rectangular windows only.