Bra Size Calculator
Find your correct bra size in US, UK, and EU sizing from your measurements.
This tool is for informational and educational purposes only. It is not a substitute for professional financial, medical, legal, or engineering advice. See Terms of Service.
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Request a ToolHow to Use the Bra Size Calculator
Getting an accurate bra size requires two measurements taken with a soft tape measure while wearing a non-padded bra or no bra at all.
- Measure your underbust. Wrap the tape measure firmly around your ribcage directly below your bust. Keep it level and snug but not tight. Enter this number in the Underbust field.
- Measure your bust. Wrap the tape measure around the fullest part of your bust, keeping it parallel to the floor. Enter this number in the Bust field.
- Choose your unit. Select inches or centimeters depending on how you measured.
- Read your results. The calculator shows your US and UK bra size plus the EU equivalent. US and UK band sizes use the same numbers but EU uses centimeters for the band.
Use the Share button to send your measurements to a shopping app or store associate.
About the Bra Size Calculator
Bra sizing uses a band number plus a cup letter. The band is derived from your underbust measurement rounded to the nearest even number. The cup is determined by the difference between your bust and underbust measurements: a 1-inch difference gives cup A, 2 inches gives B, 3 gives C, 4 gives D, and 5 gives DD.
US and UK sizing use the same band and cup letters. EU sizing uses the underbust measurement in centimeters for the band and shifts the cup letters by one (US DD becomes EU E, for example). Sister sizing lets you go up or down one band size while adjusting the cup to maintain the same cup volume.
Frequently Asked Questions
What is the difference between US and UK bra sizing?
US and UK bra sizing use the same band numbers and most cup letters up through D. The main divergence starts at DD: in the US, DD is followed by DDD or E, while in the UK, DD is followed by E, F, FF, G. The band numbers are the same in both systems, making conversion straightforward for most sizes.
Why does my bra size vary between brands?
Bra sizing is not standardized across manufacturers. A 34C in one brand may fit differently than a 34C in another due to variations in how each brand cuts cups, the elasticity of their band fabric, and their fit models. It is common to need a slightly different size in different brands. Use your calculator result as a starting point and try the adjacent sizes if needed.
What is sister sizing in bras?
Sister sizes are bra sizes that have the same cup volume but different band and cup letter combinations. For example, 34C, 36B, and 32D are sister sizes. If a 34C feels right in the cups but the band is too loose, try a 32D. If the band is too tight, try a 36B. The cup volume stays the same while the band changes.
How do I convert my US bra size to EU?
To convert a US bra size to EU, the band is converted from inches to centimeters and rounded to the nearest 5. A US 34 band is approximately 85-90 in EU sizing. The cups also shift: US A stays A, US B stays B, US C stays C, US D stays D, US DD becomes EU E, US DDD/E becomes EU F. This calculator handles the conversion automatically.