MEASURE THE GARMENT, NOT THE LABEL
Measuring & fit guides
Every guide here starts from the same premise: the size on the label is a marketing decision, and the tape measure is not. Learn to read a shirt in numbers and every size chart on the internet becomes optional.
Last verified: 26 August 2026
A shirt has real dimensions — chest, length, shoulder, sleeve — and they never argue back. These guides teach the flat-measurement method ShirtMath itself uses (the same definitions the methodology page and the scanner work from), then apply it: what each measurement means, how to take it without ruining it, and how to judge fit from the numbers instead of the letter on the tag.
Every guide, and what it answers
How to measure a shirtAll eight points of measure for tops, laid flat, one standard — the master guide the others build on.START HERE
Pit to pit measurementThe single most useful number on a shirt: what it is, how to take it, and what each value means in real sizes.THE FLAT CHEST MEASUREMENT
How to measure sleeve lengthThe garment method and the body method give different numbers. That difference is the whole confusion — explained.GARMENT VS BODY
How should a shirt fitFit principles tied to actual measurements — where a shirt should sit, in inches, not vibes.FIT, IN NUMBERS
Is my shirt too small?Concrete diagnostic checks you can run in a mirror in two minutes, each traced to a measurement.THE DIAGNOSTIC
What your shirt size means16 34/35, M, 42, XL — four different sizing languages on one rack, decoded.THE DECODER
Vanity sizingWhy a Medium isn't a measurement, what the published numbers show, and what to do instead.WHY THIS SITE EXISTS
Prefer tables to prose? The size charts hold the reference grids, and the tools turn a measurement you already have into a size. If you buy blanks, the blank tee comparison puts eight styles' published specs side by side.
More in this section
How to Measure a Dress: Bust, Waist, Hip and LengthMeasure a dress flat, not on a body.
How to Measure Inseam: The Flat Garment MethodThe inseam is the distance from the crotch seam straight down the inside leg to the bottom hem.
How to Measure Pants: All 8 Points of Measure, FlatEvery point of measure on a pair of trousers, taken flat — waist and rise through to inseam and outseam.
How to Measure Shoe Size at Home: Paper, Pencil, RulerPaper, a pencil and a ruler: trace both feet, measure the longer one, and read it against a conversion chart.
How to measure sunglasses: lens, bridge and temple mmFour measurements describe a sunglasses frame, all in millimetres: lens width, bridge width, temple length and total frame width.
Sunglasses Size Guide: Read the Three Frame NumbersThe three numbers printed inside a temple arm, and how to read them off a frame you already own.
What the numbers on sunglasses mean: 52-18-140 decodedThe three numbers inside a sunglasses arm are millimetres: lens width, then bridge width, then temple length.
Or skip the tape measure. Photograph a shirt you own and ShirtMath measures it for you, then finds garments that match its numbers.
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