Pit to Pit Measurement

Pit to pit is the width of a shirt measured straight across the chest, from one armpit seam to the other, with the garment laid flat. It is a garment measurement, not a body measurement — the tape touches the shirt, never the person — and doubling it gives an approximate chest circumference. A pit to pit measurement ignores the size label entirely, which is why resellers rely on it: on published blank specs a unisex Medium runs 20.0–20.5″ pit to pit and a Large 22.0–22.5″, while a ladies’-cut Medium can be 3″ narrower at the same letter.

You need a hard flat surface, a tape measure, and about a minute. The method is the one ShirtMath’s own measuring methodology applies to every garment: flat, in inches, seams smoothed, nothing stretched.

There are two conventions for where the tape crosses. Resellers usually measure right at the pit points. The apparel industry’s point of measure — the one ShirtMath’s catalog uses for chest — is “Lay flat, measure straight across 1″ below the armholes, seam to seam.” The lines sit an inch apart and give close but not identical readings. Which you pick matters far less than never switching: fit comparison works by subtracting one shirt’s numbers from another’s, and shirts measured on different lines add error that belongs to your technique, not the shirts. Pit to pit is one of eight points of measure for tops — the full set is in how to measure a shirt.

The standard is flat on a hard surface, seams smoothed, nothing stretched — and both halves matter. A rippled shirt reads narrow, because the tape travels over hills instead of a straight line; a stretched shirt reads wide, because jersey knit gives under even light tension. Smooth it flat, then take your hands off before you read the tape.

Pit to pit is a property of the shirt. Wrapping a tape around your own chest produces a body circumference — related to the garment number only through wearing ease, since a shirt must be bigger around than the body inside it. A listed 22″ pit to pit is the shirt lying flat — roughly a 44″ garment circumference, not a promise about what chest size wears it comfortably.

The armpit junction is not a point; it is a small lump of fabric several stitches wide, and “seam to seam” can honestly mean outer edge to outer edge or stitch line to stitch line. Add the at-the-pit versus inch-below choice, and two careful people can measure the same shirt measurably apart. None of these is the wrong technique; using different ones on shirts you intend to compare is. Pick a convention and hold it.

The table maps flat chest widths to sizes using the published specs of the eight blank tee styles in ShirtMath’s catalog, printed as-is.

First, the unisex styles agree more than sizing folklore suggests — from S to 2XL they span 1.0″ or less at any letter. Second, the letter still is not a measurement: bring in a ladies’ cut or another era of garment and the same letter means a different shirt — the pattern vanity sizing documents with published numbers. The t-shirt size chart holds the full grid including lengths; which blank runs biggest ranks these eight styles edge to edge.

Doubling pit to pit approximates the garment’s chest circumference: a shirt is a flattened tube, so width times two is distance around. The approximation assumes equal front and back panels and ignores fabric thickness at the folds — good enough for comparing shirts, not a substitute for a body measurement.

The bigger drift is that a shirt’s width changes along the torso, so one doubled number describes only the chest line. The published specs show all three shapes at once: a Gildan G500 Medium is nearly a straight tube (20.0″ chest, 19.51″ hem sweep), a Comfort Colors C4017 Medium flares outward (20.5″ chest, 21.46″ hem), and a ladies’ G500L Medium tapers hard (17.5″ chest, 15.71″ hem). Two shirts with the same pit to pit can carry very different rooms at the waist.

That drift feeds a live argument. Reselling groups periodically circulate posts titled some version of “stop using pit to pit measurements for clothes,” and the frustration underneath is consistent: shirts listed at the same width fit differently on arrival. Look closely and each complaint is a technique failure — measured at the pit versus an inch below, tape pulled taut versus laid flat, a flat garment width read as a body size. The measurement itself is fine; it is the most transferable single number a garment has, because it needs no fitting room and no trust in a label. The honest criticism is narrower: one number cannot carry length, shoulder, or sleeve, so identical pit to pit does not mean identical fit. That is an argument for measuring more points, not for abandoning the one that works.

eBay, Depop, and vintage sellers list pit to pit because the buyer cannot try the shirt on and, on older stock, the tag has often drifted from the garment or been cut out entirely. A flat width and a body length survive shipping, decades, and brand extinction; a letter does not, and any buyer can verify the numbers against a shirt already in their closet.

The search “what size is 22 inch pit to pit” has a direct answer in published specs: 22.0″ flat is a Large in six of the eight blank styles in ShirtMath’s catalog; Comfort Colors’ C4017 Large runs 22.5″, and on the ladies’ G500L, 22″ falls between XL (21.0″) and 2XL (23.0″). Doubled, it is roughly a 44″ garment circumference. The pit to pit converter runs this lookup for any value, and the rest of the measuring and fit guides cover the points a single width cannot.