Why club shop sizing rarely matches the label size in the rest of your wardrobe

A letter is not a measurement

Garment sizes are set by each manufacturer against its own fit block, which is a set of body measurements the brand has decided to design around. Those blocks differ between brands, between product lines within a brand and between the markets a line was originally developed for. The letter on the label therefore describes where a garment sits within one manufacturer's range rather than what body it will fit.

This is true of clothing generally, but sports merchandise is worse because the same nominal size appears in several quite different cuts. Buyers who treat the letter as portable information are relying on a standard that does not exist.

Fit categories matter more than sizes

Most ranges offer at least two cuts, one designed to sit close to the body and one designed to hang loosely with room underneath. The close-fitting version is engineered for someone whose measurements match the block exactly and is unforgiving of any deviation. The looser version accommodates a wider range of bodies and is what most buyers actually want, particularly for wearing over other clothing.

The difference between the two cuts in the same nominal size can exceed the difference between adjacent sizes in the same cut. Identifying the cut before choosing a size resolves more sizing problems than any amount of comparison between sizes.

Regional patterns are a real thing

Manufacturers develop fit blocks around the markets where a product line sells most, and those blocks reflect the population they were built from. A line originally developed for one region and sold internationally carries that pattern with it, which is why some brands run consistently smaller than others. Products made for specific regional markets can differ again, even where the design and the labelling appear identical.

This is a common source of confusion for anyone buying from a different market than usual and expecting the same fit. It is also why comparing a new purchase to an old shirt from the same club can be misleading if they came from different ranges.

Measurements are the only comparable figure

The reliable approach is to measure a garment that already fits and compare that measurement with the manufacturer's published figures. Chest width laid flat and body length from the shoulder seam are the two that determine whether a shirt will look right. Sleeve length matters for the close-fitting cuts, where a sleeve designed to grip the arm sits in a specific place and looks wrong if it does not.

Published size guides vary in quality, but a measurement in centimetres is at least a fixed quantity rather than a letter. Buyers who work this way rarely have to return anything, which is the entire argument for the additional effort.

Shirts have changed shape over time

The cut of replica shirts has moved considerably across the decades, from very loose through extremely fitted and back towards a middle position. A supporter comparing a current shirt to one bought years ago is therefore comparing two different design intentions rather than two sizes. Retro reissues complicate this further, since some reproduce the original cut faithfully and others apply a modern pattern to an old design.

Product descriptions occasionally state which approach has been taken, and where they do not, the measurements will reveal it. For a category where fit is the main reason for returns, this is the detail most worth checking before ordering.