A bra size can suggest a bust measurement, but it cannot tell you your exact body measurements. In a simple US or UK example, 34C corresponds to a 34 band and a bust about 3 inches larger: roughly 37 inches. Brand charts, rounding, and fitting methods can change that relationship. Measure yourself before using the number to shop.
Already have your measurements? Use our bra size calculator. To change a label between countries, use the international bra size converter.
Band size, bust size, and cup size: what is the difference?
- Underbust is the measurement around your ribcage directly beneath your breasts.
- Band size is the number on the bra label. It is selected using a sizing method; it is not always identical to your measured underbust.
- Bust size is the circumference around the fullest part of your bust.
- Cup size is a letter used with the band number. A cup letter alone does not specify one fixed volume or bust circumference.
How to estimate bust size from a bra label
For the simple inch-based examples below, add the cup difference to the band number: A = 1 inch, B = 2, C = 3, and D = 4. For example, 34 + 3 = 37 inches for 34C. Wacoal illustrates this band-and-cup calculation and notes that sizing methods can differ.
These calculations explain labels. They are not measurements taken from people wearing those sizes, and they should not be treated as a brand-specific fitting chart.
| Bra label | Band label | Cup difference | Estimated bust | Estimated bust in cm |
|---|---|---|---|---|
| 32B | 32 | 2 in | 34 in | 86.4 cm |
| 32D | 32 | 4 in | 36 in | 91.4 cm |
| 34B | 34 | 2 in | 36 in | 91.4 cm |
| 34C | 34 | 3 in | 37 in | 94.0 cm |
| 36B | 36 | 2 in | 38 in | 96.5 cm |
| 36C | 36 | 3 in | 39 in | 99.1 cm |
Centimeters above are calculated as inches × 2.54 and rounded to one decimal place. This converts a measurement; it does not convert a US band label into an EU band label.
What bra size is a 36-inch bust?
There is no single answer without an underbust measurement. In the examples above, both 32D and 34B have an estimated 36-inch bust, but their bands and cup volumes differ. A 36-inch bust also does not automatically mean a 36 band. Measure both circumferences, choose your sizing region, and check the resulting bra on your body.
Measure your body to check the estimate
- Place a soft tape around your ribcage directly under your bust. Keep it level and snug without forcing it tight.
- Measure the fullest part of your bust without compressing it. Avoid thick padding or bulky clothing.
- Record both numbers in the same unit and enter them in the calculator. Follow the retailer’s measuring instructions when using its chart.
- Try the suggested size and assess band comfort, cup coverage, and wire placement.
See the complete bra measurement guide or the cup size measuring guide for more detail.
Why international labels and sister sizes need a separate check
The example formula is not a universal rule for every country. US and UK labels can differ after D, and EU, French, and other systems use their own band and cup conventions. Select the system printed on your bra before comparing the regional bra size charts.
Sister sizes change the band and cup together to keep cup volume approximately similar. For example, 32D, 34C, and 36B are neighboring sister sizes in the common progression. They do not have the same band fit, and their estimated bust numbers are not identical. Use the sister size calculator when cup volume feels close but the band needs adjusting.
Check fit before keeping a bra
A comfortable band should remain level, cups should contain breast tissue, and wires should avoid digging or resting on breast tissue. Gaping can also reflect a mismatch in cup shape. Bravissimo’s fitting guide explains these checks and offers fitting help. Our common fit problems guide can help you choose what to adjust next.
Updated September 9, 2026: clarified that reverse calculations give estimates, distinguished band labels from body measurements, and replaced the mixed international measurement table. Published by Bra Size Calculator; this is educational fitting guidance, not a professional fitting assessment. Editorial policy · Report a correction.