Sizing tools
Both tools here do one thing: take a number you can actually stand behind — a flat measurement off a real shirt — and translate it into the sizes stores use. Each answer comes with its confidence level, because pretending certainty is how sizing got broken in the first place.
Last verified: 26 August 2026
These are for an individual shopper working from one garment. They run entirely in your browser, degrade to a plain reference table when JavaScript is off, and never guess: when your input sits between sizes or outside the data, the tool says so instead of rounding you into a purchase. The measurement definitions are the same ones the methodology and the scanner use, so a number taken with the measuring guide drops straight in.
Two tools, one measurement each
Not sure your measurement is good? The pit-to-pit guide covers the three mistakes that ruin it. And if you want to know why a calculator is even necessary — why the letter on the label stopped being a measurement — that story is at vanity sizing.
The best input is a photo. Scan a shirt you own and ShirtMath takes all eight measurements at once, then searches by them.
Scan a shirt