Your bra band size is the number that comes first in a size such as 75B or 80D. It tells you how big the elastic band around your ribcage should be, and it carries most of the support in a bra. This calculator turns your underbust measurement into the European (EN 13402) band size, shows the range of measurements that size covers, and lists the next band sizes up and down in case your measurement falls near an edge.
How to use the band size calculator
- Wear an unpadded, non-wired bra or no bra and stand straight with your arms relaxed.
- Measure the underbust: wrap a soft tape measure around your ribcage directly under the bust, where the bra band sits. The tape should be level all the way round and snug, but not digging in.
- Enter the number in centimetres or inches and choose the unit.
- Read your band size, the range of underbust measurements it covers, and the neighbouring band sizes.
Measure twice and use the average if the two readings differ. Breathe out normally rather than holding your breath in or out.
Band size formula
Range covered = band − 2.5 cm to band + 2.5 cm
Under the European clothing size standard EN 13402, a bra is labelled with the underbust girth rounded to the nearest 5 cm, followed by the cup letter. That is why European bands run 60, 65, 70, 75 and so on. A measurement that falls exactly halfway between two bands (for example 77.5 cm) is rounded up in this calculator, which is the usual convention for rounding to the nearest value.
The standard describes the label of the garment, not how snug it feels. Brands cut their bands to different stretch, so the band you buy can differ from the band you measure. Treat the result as a starting point and then try it on.
Worked example
You measure 78 cm under the bust.
- 78 ÷ 5 = 15.6, which rounds to 16.
- 16 × 5 = 80, so your EU band size is 80.
- Band 80 covers 77.5–82.5 cm, so 78 cm sits near the lower edge. Band 75 (72.5–77.5 cm) is the next size down, and may fit better if bras in size 80 feel loose.
In inches: 30 in is 76.2 cm, and 76.2 ÷ 5 = 15.24, which rounds to 15, giving a band of 75.
EU band sizes and the underbust range each covers
This table was generated with the same rule the calculator uses (nearest 5 cm; halfway values round up).
| EU band | Underbust range (cm) | Underbust range (inches) |
|---|---|---|
| 60 | 57.5–62.5 | 22.6–24.6 |
| 65 | 62.5–67.5 | 24.6–26.6 |
| 70 | 67.5–72.5 | 26.6–28.5 |
| 75 | 72.5–77.5 | 28.5–30.5 |
| 80 | 77.5–82.5 | 30.5–32.5 |
| 85 | 82.5–87.5 | 32.5–34.4 |
| 90 | 87.5–92.5 | 34.4–36.4 |
| 95 | 92.5–97.5 | 36.4–38.4 |
| 100 | 97.5–102.5 | 38.4–40.4 |
| 105 | 102.5–107.5 | 40.4–42.3 |
| 110 | 107.5–112.5 | 42.3–44.3 |
Things to keep in mind
- The band does the work. A well-fitting band is firm and level, sits straight across your back and stays in place when you raise your arms. Many people wear a band that is too loose.
- Band and cup go together. If you change the band, the cup volume changes too. The Sister Size Calculator shows which band and cup combinations hold the same volume, and the Cup Size Calculator finds your cup letter from the bust measurement.
- US and UK band numbers are different. They use inches and a different numbering, so a European 75 is not a 75 in those systems. This page gives the European band only. Use the Bra Size Converter (US/UK/EU/AU/FR/JP) for other systems once it is available.
- Brands differ. Some cut small, some stretch more. Always check the brand size guide before you buy.
For the complete size (band plus cup) use the European Bra Size Calculator or the bra-size-calculator.
Sources
The rule that the band is the underbust rounded to the nearest 5 cm comes from descriptions of EN 13402-3 (the bra part of the European body-measurement size standard). We did not have access to the paid standard text, so we cross-checked two public explanations. Where they differ in small details, the page says so.
- MobileFish — EN 13402 pictogram help: cup and band — checked 2026-10-15
- Wikipedia — Brassiere measurement (European sizes) — checked 2026-10-15
- Calculator.net — Bra size chart (EU/US/UK) — checked 2026-10-15
Frequently asked questions
How do I find my bra band size?
Measure around your ribcage directly under the bust, with the tape level and snug. In the European system the band size is that measurement rounded to the nearest 5 cm, so 78 cm gives a band of 80.
What if my underbust is exactly between two band sizes?
A value halfway between two bands, such as 77.5 cm, is rounded up in this calculator. In practice choose the band that feels firm and level, and try the neighbouring band in the same brand. The Sister Size Calculator shows which cup goes with it.
Is a European band size the same as a US band size?
No. European bands are in centimetres in steps of 5 (65, 70, 75…), while US and UK bands are in inches and use different numbers. This page gives the European band only.
Should I measure with or without a bra?
Measure over an unpadded, non-wired bra or with no bra, so the tape sits against your body and is not pushed out by padding.
Why does my measured band size feel too loose or tight?
The standard describes how a garment is labelled, not how it stretches. Brands cut and stretch differently, so use the result as a starting point and try the band size above or below. The Cup Size Calculator helps you pick the cup that matches a changed band.