Letter Size Conversion: S, M, L, XL

Gym shorts, underwear, t-shirts and hoodies are sold by letter, not by inches, so a waist you know perfectly well becomes a guess at the shelf. Enter your waist (for bottoms) or chest and bust (for tops) and we will give you the letter, the inch range behind it, the number size equivalent, and the men's to women's crossover.

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Here is a problem almost everyone has had at a shelf. You know your waist is 40, because your trousers say so and a tape measure agrees. The gym shorts in front of you say S, M, L, XL. The pack of underwear behind them says the same. Nothing on either label mentions an inch. This page does that translation, in both directions, for tops and bottoms.

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How letter sizing works, and why it feels random

Number sizing at least starts from a measurement: a men's 40 trouser aims at a 40 inch waist, a jacket 42 at a 42 inch chest. Letter sizing throws that away and sorts everyone into five or six buckets instead. Each bucket covers a range of about two to four inches, which is why two people who wear different trouser sizes can both be a Large, and why the same person can be a Medium in one brand and a Large in another.

The buckets themselves are a convention rather than a standard. Nothing forces a brand to agree with anyone else, and nothing forces them to publish the inches behind their letters. When a brand does publish them, those numbers beat any general chart, including this one.

The method

bottoms: your waist in inches, matched to the letter band that covers it
tops: your chest (men's) or bust (women's), matched the same way
a measurement between two published bands resolves to the nearer one

The bands below are the standard published ranges. Where a garment chart on this site already covers the same measurement, this page uses those exact numbers, so our pages never disagree with each other: women's bottoms follow the ladder in our pant size conversion, women's tops follow the bust ladder in our dress size calculator, and men's tops follow the casual letter column in our jacket size conversion.

Worked example

You have a 40 inch waist and you are looking at gym shorts. On the men's chart, 40 is the bottom of the XL band, which covers 40 to 42 inches. So you want an XL. Note what you should not do: the band below, L, stops at 38 inches, so an L is two inches short and will not fit, even though you are sitting at the very bottom edge of XL. Useful extra: the same 40 inch waist in women's sizing is an XXL, not an XL, which is why letters cannot be carried from one department to the other.

Men's letter sizes

LetterWaist (bottoms)Chest (tops)Number size
XS26 to 27 in32 to 34 inwaist 26 to 27, jacket 34
S28 to 30 in35 to 38 inwaist 28 to 30, jacket 36 to 38
M32 to 34 in39 to 40 inwaist 32 to 34, jacket 40
L36 to 38 in41 to 42 inwaist 36 to 38, jacket 42
XL40 to 42 in43 to 44 inwaist 40 to 42, jacket 44
XXL44 to 46 in45 to 48 inwaist 44 to 46, jacket 46 to 48
3XL48 to 50 in49 to 52 inwaist 48 to 50, jacket 50 to 52

Women's letter sizes

LetterWaist (bottoms)Bust (tops)US number size
XS24 to 26 in32 to 33 in0 to 2
S26 to 28 in34 to 35 in4 to 6
M28 to 30 in36 to 37.5 in8 to 10
L31 to 34 in39 to 40.5 in12 to 14
XL35 to 38 in42 to 44 in16 to 18
XXL40 to 43 in46 to 48 in20 to 22

A men's medium is not a women's medium

This is the single most useful thing on the page, and it is why the underwear aisle confuses people. The letters are anchored to different bodies. At the same waist measurement, a men's letter usually sits one step below the women's letter: a 32 inch waist is a men's M but a women's L, a 36 inch waist is a men's L but a women's XL, and a 40 inch waist is a men's XL but a women's XXL.

So when you buy a unisex t-shirt, a men's sweatshirt to wear oversized, or you are shopping across departments for someone else, the letter does not travel. Convert through the measurement instead, which is what the tool above does automatically. Unisex garments, by the way, are almost always cut on the men's block, so a woman buying unisex usually wants one letter down from her usual women's size.

Where the letters lie the most

Two places, both worth knowing. First, waistbands with elastic. A pack of underwear or a pair of gym shorts labelled L often stretches across a much wider range than the chart implies, which is why brands feel free to disagree: the elastic hides the error. Second, the edges of a band. A 42 inch waist sits at the very top of men's XL, so there is nothing left before the next size and a brand cut slightly small will not close. The bands also have gaps between them, which catches people out: men's L stops at 38 and XL starts at 40, so a 39 inch waist belongs to neither cleanly, and a 40 inch waist cannot drop to an L no matter how generously it is cut. Sitting mid band is the comfortable place to be, and the tool tells you where in the band you land for exactly that reason.

The durable habit is the same one that fixes every other sizing problem: know your measurement in inches, and read each brand's own chart against it. The letters change from shop to shop. The inch does not.

Frequently asked questions

What size is a 40 inch waist in shorts?

In men's letter sizing a 40 inch waist is an XL, since the men's XL band covers roughly 40 to 42 inches. You are at the bottom of that band, so a brand that runs generous might fit you in a large. In women's letter sizing the same 40 inch waist is an XXL, because the two systems are anchored to different bodies.

What waist is a men's medium?

About 32 to 34 inches for shorts, underwear and sweatpants. The usual men's ladder runs S at 28 to 30, M at 32 to 34, L at 36 to 38, XL at 40 to 42, and XXL at 44 to 46. Brands shift these by an inch or two, and elastic waistbands stretch further still, which is why the same person can be a medium in one brand and a large in another.

Is a men's medium the same as a women's medium?

No, and this is the most common letter sizing mistake. At the same measurement a men's letter usually sits one step below the women's letter: a 32 inch waist is a men's M but a women's L, and a 36 inch waist is a men's L but a women's XL. Convert through the measurement rather than carrying the letter across.

What size is a unisex t-shirt?

Unisex garments are almost always cut on the men's block, so a unisex medium is a men's medium, fitting a chest of roughly 39 to 40 inches. A woman buying unisex usually wants one letter below her usual women's size, and should expect a straighter cut through the waist and a wider shoulder.

How do I measure for letter sizing?

For bottoms, wrap a soft tape around where the waistband actually sits, which for most shorts and underwear is at or just below the navel rather than at your narrowest point. For tops, measure the fullest part of your chest or bust with the tape level. No tape? Use a piece of string, mark where it overlaps, and lay it against a ruler.

Why do letter sizes vary so much between brands?

Because there is no standard behind them. A letter is a bucket a brand chooses, not a measurement, and each bucket covers two to four inches, so there is room to disagree even in good faith. Elastic waistbands hide the difference further. When a listing publishes the actual inches behind its S, M and L, trust those over any general chart.

Should I size up if I am at the top of a band?

Often, yes, for anything without stretch. If your waist is 42 and the XL band is 40 to 42, you have no room left before the next size, so a brand running slightly small will not fit. Sitting in the middle of a band is the comfortable place. The tool above tells you where in the band you land for that reason.

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