About FramingMath

Why this exists

It started with one mat. Working out the border so a print sits centered — then accounting for the quarter-inch overlap, the slightly larger bottom border, and the frame size that all of it adds up to — meant a notepad, a calculator, and a couple of mistakes with expensive board.

The tools online weren't much better: downloadable Excel files, single-purpose pages that only did one size, or calculators that gave a number with no picture of what it meant. So I built the thing I wanted — something that does the framing math instantly, shows you the result, and works on a phone at the framing table.

What FramingMath does

The goal is a toolset that's:

• Accurate — formulas tested against known correct values, to the 1/16 inch or the millimeter.
• Instant — results as you type; nothing to install or download.
• No sign-up — no account, no email wall, no paywall.
• Shareable — every result has its own link that reopens the exact layout.
• Bilingual on units — US sizing throughout with full metric support, side by side.

What makes it different

Most framing calculators stop at a number. FramingMath adds the parts that actually help you commit to a cut:

• a live SVG preview of the finished piece, redrawn as you change the numbers;
• shareable, deep-link URLs — answer a question or save a layout by sending a link that opens it pre-filled;
• no spreadsheet downloads — it's a web page, not a file to manage;
• a mobile-friendly layout for use right at the workbench.

How the math is verified

Framing math is unforgiving: a sixteenth of an inch in the wrong direction means a window that shows a white sliver of paper, or a mat that will not sit in the frame. So the calculators are not trusted on sight.

• The formulas are pinned by an automated test suite, which fixes each one to known values and covers the awkward cases: overlaps in sixteenths, a zero overlap, metric input to the millimeter, and negative or non-finite entries, which are rejected rather than quietly returning a number.
• The method is written down. Every calculator page carries a "how it works" section and a worked example with real numbers, so you can follow the arithmetic by hand and check the tool against it rather than taking a number on faith.
• Rounding is stated, not silent. By default results land on 1/16 inch or the nearest millimeter — the precision you can actually cut to — and the page says so when a value has been rounded to get there. Switch on Decimals for the exact figure.
• Conventions are labeled as conventions. The ¼″ overlap, bottom-weighting and the quarter-inch reveal are framing-trade practice, not published standards — the mat-border and double-mat guides say so, and say when to depart from them, rather than presenting a number as a rule.

Start here

Try the flagship multi-opening mat calculator for collage and multi-photo layouts, or read the framing & matting guides to brush up on borders, bottom-weighting and double mats. Found a bug or have a feature idea? Email support@framingmath.com.