Clothing Size Converter

Two different kinds of number

This is the thing that makes clothing sizing so much more confusing than it needs to be, and almost nobody says it out loud: men’s and women’s sizes are not the same kind of number.

A men’s size is a measurement. A 40 jacket is a 40-inch chest. An EU 50 jacket is a 100 cm chest — the EU number is literally the chest in centimetres divided by two. A 16 shirt is a 16-inch neck, and an EU 41 shirt is a 41 cm neck. You can compute any of these from any other, exactly, because the inch is exactly 2.54 cm.

A women’s size is an ordinal. A US 10 is not ten of anything. It is a position in a sequence, and the sequence was never derived from a measurement. Nor is a UK 14, or an EU 40.

One consequence is immediate: the men’s panel of this calculator is doing arithmetic and the women’s panel is not, and the tool behaves differently in each because the underlying questions differ.

There is a near-miss worth knowing in the men’s side too. EU 50 is a 100 cm chest, which is 39.4 inches — not 40. The familiar “EU 50 equals US 40” pairing is over a centimetre out, because each system rounds to round numbers in its own units and those do not line up.

Why women’s conversion is a convention

If a US 10 measures nothing and a UK 14 measures nothing, then converting between them cannot be arithmetic. What actually exists is a trade habit: add four for the UK, add thirty for the EU.

These offsets are consistent enough to be useful and are not derived from anything. This calculator applies them and flags every such answer as a convention, because the alternative — printing “US 10 = UK 14” in the same typeface as “40 inches = 101.6 cm” — implies a precision that does not exist.

The deeper reason the numbers cannot be pinned down is that they drift. Labels have moved over decades in the direction of larger bodies wearing smaller numbers, so a size taken from an older garment or an older chart will not match a current one, and two current brands need not match each other either. That is a commercial choice rather than a measurement error, and no conversion table can correct for it.

What follows practically: for women’s clothing, the brand’s own size chart is the authority, every time, and your measurements are the input to it. A converted label is a starting point for which chart row to read.

A label is a band, not a measurement

Even within one brand, a size does not correspond to a body — it corresponds to a range of bodies. A US 10 typically covers a bust of about 91 to 94 centimetres, which is three centimetres of different people wearing the same number.

That has two consequences the calculator surfaces rather than hides.

First, a measurement that lands on a band boundary matches two sizes equally well, and the tool says so instead of choosing. A converter that returns one answer at 91 cm has made a decision for you and not mentioned it.

Second, a measurement outside every published band returns nothing rather than the nearest size. Extrapolating past the end of a table that was fitted to a population is how a tool starts producing confident nonsense.

Letter sizing compounds this by throwing away information the number already had. One letter covers two or three ordinals — M is roughly US 8 and 10 — and the boundaries are not agreed, so US 4 appears in both the XS and S ranges depending on whose chart you read. A garment sold only as “M” is the coarsest description of fit in the shop.

EN 13402 already solved this

There is a European standard for this, and it works by refusing to invent a number at all.

EN 13402 designates a garment by the body measurements it fits, in centimetres. A garment for a 92 cm bust, 74 cm waist and 99 cm hip is designated 92-74-99. There is nothing to convert, nothing to look up and nothing to argue about — the designation is the measurement, in the same way a men’s collar size is.

It also sidesteps the drift problem entirely. A measurement cannot be inflated for marketing reasons, because 92 centimetres is 92 centimetres in any decade.

Adoption has been partial. Some European retailers print the pictogram or the measurements alongside the traditional number; most still lead with the ordinal, because that is what shoppers recognise. So the standard exists, solves the problem completely, and is largely ignored — which is why the rest of this page is necessary.

The practical use is as a common currency. If you know your measurements in centimetres, you can read any brand’s chart in any country without going through a numbering system at all, and that is the most reliable way to buy clothing across markets.

Measuring yourself properly

Since measurements are the only reliable input here, they are worth taking carefully. The definitions come from ISO 8559 and are more specific than most people assume.

• Bust or chest: around the fullest part, with the tape level all the way round and passing under the arms. Level matters more than most people expect — a tape that drops at the back reads several centimetres large.
• Waist: at the natural waist, which is the narrowest point, not where a waistband sits. Bend sideways and the crease marks it.
• Hip: around the fullest part, usually about 20 cm below the waist, with feet together.
• Neck: around the base, with one finger between the tape and the skin. That finger is the standard allowance and it is why a collar measured tight will feel wrong at the right size.

Two habits that improve the result. Measure over the underwear you would actually wear with the garment rather than over clothes, since a jumper adds two centimetres and a coat considerably more. And take each measurement twice — a tape that has twisted or ridden up gives a consistent-looking wrong answer, and the second reading catches it.

Finally, expect your own measurements to move. Ordinary daily and cyclical variation is a centimetre or two, which is a meaningful fraction of a size band. A single measurement is a starting point rather than a fixed property, which is also the honest reason to treat any size chart as advice.

Related calculators

Other sizing systems that do not agree with each other:

More in Everyday, or browse all calculators.

Sources and methodology

Only two things here are standardised: the measurement definitions, and the European convention of designating a garment by the body it fits. The numbering systems themselves are trade conventions that no body maintains, which is exactly why this page separates the parts it can derive from the parts it can only report.

• EN 13402 — Size designation of clothesEuropean Committee for Standardization (CEN) · verified 2026-09-07 · The European standard that designates a garment by the body measurements it fits, in centimetres — the approach this page treats as the unambiguous fallback, and the reason a designation needs no conversion
• ISO 8559 — Size designation of clothes: garment construction and anthropometric surveysInternational Organization for Standardization · verified 2026-09-07 · The definitions of the bust, waist, hip, chest and neck measurements used throughout, and the principle that a size designation should derive from body measurements rather than from garment dimensions
• NIST — the international yard and pound agreement of 1959National Institute of Standards and Technology, US · verified 2026-09-07 · The inch as exactly 2.54 centimetres — the only exact arithmetic anywhere in this subject, and what makes the men’s chest and collar conversions genuine conversions rather than conventions