Shirt size calculator

These are the 53 specification rows the calculator searches, printed. Chest is the flat width across the front; double it for the circumference inside the garment. Sleeve is deliberately absent, for a reason worth its own section below.

Read across a row and the problem with letter sizing is visible: a Medium is 20.0" in five runs, 20.5" in two, and 17.5" in the ladies’ cut of the same Gildan shirt. That last gap is 3" flat, 6" of circumference, inside one letter. Vanity sizing is how those decisions drifted apart.

There is no sleeve column in the tables above, and leaving it out is the honest choice rather than a gap. Here is the evidence, from our own specification rows, at one single size:

Gildan’s G500 lists 17.0" and Hanes’ 5250T lists 8.38" for a sleeve at the same size M. Neither is wrong. They are measuring different distances and publishing them under the same word: one starts at the centre of the back of the neck and travels across the shoulder before it reaches the arm, the other starts where the shoulder seam meets the sleeve. Roughly a factor of two, in a column most size charts label simply “sleeve”.

Put those in one table and you publish a comparison that is false. So this calculator does not use sleeve, and the tables above do not show it. If you want to compare sleeves across brands, you first have to know which convention each one used, which is what how to measure sleeve length is for.

No model, no fitted curve, no learned mapping from bodies to garments. It holds the 53 published rows above, subtracts your chest measurement from each published chest, and reports the nearest one along with how far off it was. Three verdicts are possible.

The half-inch window tracks the brands’ own stated variance — ±0.3" on seven of these styles, ±0.8" on the garment-dyed C4017. Inside that window a spec sheet and your tape do not disagree in any way you could act on. Outside it, they do, and it says so rather than rounding you into a purchase. Body length and shoulder, if you enter them, are only ever used to confirm or contradict the chest answer; they never override it.

Height and weight describe a body. A size chart describes a garment. Between the two sits wearing ease — how much air the pattern maker left — and that is a style decision no body measurement can recover.

The gap is measurable in the tables above. Most runs grade 2.0" of flat chest per letter, which is 4" of circumference; the Next Level 3600 steps 1.5" up to Large, and the ladies’ G500L steps 1.0" then 1.5". Two people at identical height and weight routinely differ by more than a full step across the chest. That is why the second mode returns a band of three letters and prints the span of published inches they cover, instead of one letter it cannot justify. The centre of that band comes from a weight table we chose; it is a convention, and it is the only number in this tool that is not a published specification.

Now that the numbers above are in front of you, this is the useful moment to run one: