Pit to pit vs chest: why the two numbers differ

Two measurements, two objects

Pit to pit belongs to the garment. The shirt lies buttoned on a table and someone measures across the front, from one underarm seam to the other. It is a width, and it covers the front panel only.

Chest belongs to you. The tape goes under your arms, over your shoulder blades and across the fullest part of your chest, and it comes back to where it started. It is a circumference.

The trouble starts because size charts use the word chest for both. One brand writes “Chest 21” and means the shirt, flat. Another writes “Chest 40” and means the body it was cut for. A third writes “Chest 42” and means the shirt again, this time all the way around. All three can be describing the same medium.

The conversion

Double the pit to pit and you have the distance around the shirt at the chest. 21 inches flat is 42 around. That is the whole of the arithmetic.

What it gives you is the shirt’s chest, not yours. The gap between the two is the room you have to move in, and tailors call it ease.

How much room a shirt should leave

A shirt that measured exactly what you do would fit like a wetsuit. You need space to breathe, to reach for something, to sit down without the buttons taking the strain. How much depends on what the shirt is for.

The knit row starts lower because a T-shirt stretches and a poplin shirt does not. An inch of room in jersey is comfortable. An inch of room in a woven oxford is a shirt you cannot raise your arms in. Jackets need the most because they go on over everything else.

These are the ranges our own scoring starts from. Once you tell us about a shirt you own and like, we stop using them and use yours.

Working out which one a chart means

Most charts do not say. The numbers give it away.

• Between about 17 and 27, for an adult: a flat measurement of the garment. This is what almost every secondhand seller gives, and what Japanese and workwear brands tend to publish.
• Between about 34 and 50, climbing two inches a size: usually your body. Look for the words “to fit” or “body measurements” near the table.
• Between about 38 and 56, where the medium is four or more inches bigger than the chest a medium is normally sold to: the garment, measured around.
• In centimetres the same three bands are roughly 43 to 69, 86 to 127, and 96 to 142.

Why we keep them apart

Every measurement we hold is filed under the ruler it was taken with. A flat width is stored as pit to pit. A circumference is stored as chest. We never double a number on a guess, and when a brand’s chart does not make clear which it is, that chart is left out rather than interpreted.

It costs us some brands. It also means that when a page says a shirt leaves you four inches of room, the four inches came from two measurements that were actually comparable. How the matching works has the longer version.