About ShirtMath
ShirtMath is a fit search engine. Instead of asking what size you wear, it asks what actually fits you — the shirt in your closet whose numbers you already trust — and then compares those numbers against the measurements retailers publish for their own garments.
Last verified: 26 August 2026
What the site does
You can measure a shirt you own from a single photo, or type its measurements in by hand. ShirtMath then searches its catalog of garments — indexed from retailer-published product data — and shows you, in inches, how each one differs from your reference shirt. Every purchase happens on the retailer's own site; ShirtMath sells nothing directly.
Where the numbers come from
Catalog measurements come from what sellers themselves publish for each garment. Measurements marked “estimated” are projections and are labeled as such — they are never presented as tape measurements. When a merchant publishes no usable measurements for a garment, ShirtMath leaves it out of fit matching rather than inventing numbers. The photo scanner is experimental: it leaves a measurement blank when it cannot read it confidently, and we publish its accuracy honestly on the methodology page.
Independence
ShirtMath is an independent project. Some outbound links are affiliate links, which means ShirtMath may earn a commission when you buy through them, at no extra cost to you. Affiliate status never changes how garments are ranked or which measurements are shown — ranking is driven by fit math, not commissions. The affiliate disclosure sets this out in full.
Getting in touch
Corrections to a measurement are the most useful message anyone can send. The contact page explains what to include, and ShirtMath for Brands covers the retailer side of the same fit engine.
The numbers are the product. Scan a shirt you already own and see what the catalog says about it.
Scan a shirt