Bra size conversion chart across 7 systems

Find your size in one system, then read across. Bands follow simple rules from one system to the next. Cup letters are the same everywhere up to D, then the UK adds DD, FF and GG, and the US adds DD and DDD.

Every size below is computed by the conversion code inside Ruban Size, from EN 13402-3, the European standard for bra labels, and the usual conversions. They are approximate, and past D the brand's own chart matters most.

Bra size conversion chart

For any other size, convert the band and the cup separately with the two tables below.

Band sizes in 7 systems

The rules behind it:

• EU: the underbust in centimeters, rounded to the nearest 5 (EN 13402-3). A 75 band covers an underbust from 72.5 to just under 77.5 cm.
• FR: the EU band plus 15. An EU 75 is a French 90.
• IT: counts from 0 at EU 60, one step per 5 cm.
• UK and US: inches, in steps of 2, with EU 70 at 32. Each 5 cm of band is 2 in.
• AU: the UK band minus 22.
• JP: the EU band, written after the cup (C75).

The UK band is a label, not your underbust in inches. A 70 cm underbust is 27.6 in, and its band is 32.

Cup letters in 7 systems

EN 13402-3 sets the cup from the difference between bust and underbust: AA for 10 to 12 cm, then one letter per 2 cm.

So UK DD and US DD are the same cup, EU E. After that they split: EU F is UK E and US DDD, and EU H is UK FF. The engine stops at K, a difference of 32 cm and more.

Worked through once: an underbust of 76 cm and a bust of 93 cm give a 75 band (76 rounds to 75) and a 17 cm difference, a C. That is 75C, or 34C in the UK and US.

The bra size calculator runs the same code on its own page. For the measuring itself, see how to measure your bra size.

Sister sizes

A sister size keeps the same cup volume on a different band: one band down and one cup up, or one band up and one cup down.

Sister sizes help when a size is sold out or the band feels wrong, but they fit differently: the cup holds the same, the band is tighter or looser. More in bra sister sizes explained.

Why bra conversions are approximate

Bands convert cleanly. Cups are where charts differ, especially past D, where each brand picks its letters.

Two honest charts can be a cup apart. A chart that counts its cups from the band number starts its 75A at an 85 cm bust, a 10 cm difference that EN 13402-3 calls AA; at 76 and 93 cm, the standard gives 75C and that chart 75D. Ruban Size's Bras template follows the standard (75A from 87 to 89 cm, 75C from 91 to 93 cm), and Find my size reads the bust for the middle of the band, so 76 and 93 cm give 75C there too. For a given bra, the brand's chart wins.

How a store should present bra sizes

1. Label sizes in your brand's own system (75C, or 34C), since that is what is printed on the bra and on the variants.
2. Show other systems on their own rows or columns, marked as size systems, with a switch, or give them in the answer of a size finder. The first system shown follows the country: US in the United States, UK in the United Kingdom and Ireland, EU elsewhere.
3. Give underbust and bust ranges with a cm/in switch.
4. List the sister sizes next to the answer.

How Ruban Size does it

The Bras template lays out EU bands 70, 75 and 80 in merged cells, the underbust range of each band, and cups A to D with their bust ranges, under one line: "Find your band from your underbust, then your cup from your bust." The Maternity and nursing bras template runs bands 75 to 90 with cups B to E.

Find my size for bras asks for underbust and bust. When the chart's sizes are bra sizes, the answer adds two lines, here for a 75C:

• "The same size in other systems: FR 90C · IT 3C · UK 34C · US 34C · AU 12C · JP C75"
• "Sister sizes (same cup volume): 70D · 80B"

When the chart uses letters (S, M, L), like the Sports bras template, the answer says "Your bra size from these measurements (EN 13402)" and lists the size in all seven systems, with its sister sizes.

Questions

Is a UK DD the same as a US DD?

Yes, both are the EU E cup, a bust 20 to 22 cm larger than the underbust. After that they split: UK E is US DDD, which is EU F.

What is a 34C in European sizes?

75C. It is also 90C in France, 3C in Italy, 12C in Australia and C75 in Japan.

What are sister sizes in bras?

Sizes with the same cup volume on another band: one band down and one cup up, or one band up and one cup down. The sister sizes of 34C are 32D and 36B.

Why are French bra sizes 15 higher?

French bands add 15 to the EU band: an EU 75 is a French 90. The cup letter stays the same.