What number is a small, medium or large?

Each letter covers two US numbers in women's clothes: S is 4 to 6, M is 8 to 10, L is 12 to 14. That holds for dresses and tops in Ruban Size's templates. It doesn't hold everywhere: swimwear and lingerie use other numbers for the same letters, and men's letters are defined by measurements, not by numbers.

All values below are copied from the app's templates, typical charts that each store replaces with its own. Inches are centimeters divided by 2.54.

Women's letter sizes to numbers

From the Dresses template, body measurements:

The Women's tops template uses the same letters and numbers, from XS to XL. In both, the UK number is the US number plus 4 and the EU number the US number plus 32. The waist and hips of each size, and the petite and plus ranges, are in women's clothing sizes: US, UK and EU compared.

How to read it

1. Find your letter, or your number, in the system you know.
2. Read across: an M is a US 8 to 10, a UK 12 to 14, an EU 40 to 42.
3. Check the measurement. A letter is a range of bodies, here 90 to 95 cm of bust for an M. Your bust, waist and hips decide, not the label you wore last time.

If you're a US 10, you're at the top of M. If you're a US 11, a number these charts don't print, you're between M and L, and the measurements settle it.

The same letter, a different number

In practice, a letter belongs to a chart. Four of the app's women's templates give four answers for the same letters:

The briefs template gives one number per letter, two apart, and its M is a US 6 (EU 38), for a waist of 68 to 73 cm and hips of 94 to 99 cm. The dresses M is a US 8 to 10, for a waist of 72 to 77 and hips of 98 to 103. Same letter, different body. The swimwear template ends at XL = US 16 and starts at XS = US 2. Petite letters carry a P (XS P, M P) and run down to XXS P, a US 00.

Plus sizes are their own range again: 1X is a US 14W to 16W, 2X 18W to 20W, 3X 22W to 24W and 4X 26W to 28W in the Plus-size template. An XL (US 16 to 18) and a 1X (14W to 16W) overlap in numbers but not in bodies: the XL is a bust of 102 to 108 cm, the 1X a bust of 42 to 44 in, which is 106.7 to 111.8 cm.

Men's letters go by chest

Men's templates don't pair letters with numbers. They give each letter a chest, and for shirts a neck. From the Men's T-shirts and Men's shirts templates:

The numbers men do buy by are other garments. Pants numbers are the waist in inches: a men's M waist of 32.3 to 35.0 in is where pants 32 and 34 sit in the Men's pants template. Suit numbers follow the chest: the M chest, 96 to 103 cm, runs across suits UK/US 38 to 42 (EU 48 to 52) in the suits template. That spread is why suit charts use numbers, not letters. The full men's tables are in men's clothing sizes compared.

XXL, 2XL and beyond

XXL and 2XL name the same step, written two ways; 3XL is the next one. Ruban Size's templates use both spellings: XXL in Dresses and Men's T-shirts, 2XL and 3XL in Scrubs, where 2XL is a chest of 119 to 126 cm and 3XL 127 to 134 cm.

Why there's no single conversion

The European label standard, EN 13402, describes a size by the body measurements it fits, in centimeters, and that is the part of a chart that travels from brand to brand. In practice, letters and numbers are each brand's grouping of those measurements, which is why a medium isn't the same size at every brand.

How a Shopify store should show letters and numbers

1. Your variants' labels as the sizes, letters or numbers, in the first row or column.
2. The other systems on rows of their own, marked as size systems, with a switch above the table, so shoppers read the one they know.
3. Measurements on every chart, so a shopper can check a letter against a body.
4. One chart per garment type. Copying the dress line onto briefs or swimwear gives wrong numbers.
5. The first system by country: US in the United States, UK in the United Kingdom and Ireland, EU elsewhere.

How Ruban Size does it

The Women's tops template puts the letters across the top and the US, UK and EU numbers on three rows marked as size systems. Shoppers see one system at a time and switch above the table; the first one follows their country, and their choice is remembered. In the size chart editor, a row headed US, UK or EU is read as size labels, so 8-10 stays a label and is never converted like a measurement.

Find my size compares the shopper's chest, waist and hips with the chart and answers in the chart's own label, "Your size: M". "Select this size" then picks the product's variant, whether the variant is named by the letter or by the chart's first size system: on a chart whose first system is US, a variant named M or 8-10 is found either way. The size already chosen on the product page is highlighted in the guide.

Questions

What number is a women's medium?

A US 8 to 10, UK 12 to 14 and EU 40 to 42 in Ruban Size's Dresses and Women's tops templates, for a bust of 90 to 95 cm (35.4 to 37.4 in).

Is a size 8 a small or a medium?

A medium on dresses and tops (M is US 8 to 10). On the Lingerie briefs template, a US 8 is an L, which is why every garment needs its own chart.

What size is a men's large?

A chest of 104 to 111 cm (40.9 to 43.7 in) in the Men's T-shirts template, and a neck of 41 to 42 cm (16.1 to 16.5 in) in the Men's shirts template.

Is XXL the same as 2XL?

Yes, they are two ways of writing the same step. 3XL is the size after it.