UK Bra Size Calculator
Step 1: Measure Underbust
Wrap a soft tape measure around your ribcage, just below your breasts. Keep it snug but comfortable, exhaling normally. Note the measurement in inches or cm.
Step 2: Measure Bust
Measure around the fullest part of your bust, keeping the tape parallel to the floor and not too tight. Stand straight with arms at sides.
Step 3: Enter Measurements
Use the form below to input values. Switch units if needed for accuracy.
Your Suggested UK Bra Size
Related Sizes to Try
These suggestions account for typical UK sizing. Try on for final fit, as body shape varies.
How Sizing Works
Band size comes from rounding the underbust measurement to the nearest even number, often adding 4-5 inches for comfort in older methods, but modern approaches use direct snug measurement rounded up. Cup size derives from the difference between bust and band: 0-1 inch is AA, 1 inch A, 2 inches B, up to G or beyond for larger differences. UK standards align closely with international but prioritise even band numbers like 30, 32, 34. Factors like breast shape or time of day can influence readings by up to an inch.
Frequent Questions
What if my measurements fall between sizes?
Opt for the closer band and adjust cup accordingly. For example, a 33-inch underbust might fit a 32 or 34 band; test both for support.
Do UK sizes differ from US or EU?
UK band sizes match US, but cups can vary slightly by brand. EU uses cm and different cup lettering, so convert carefully when shopping abroad.
How often should measurements change?
Recheck every six months or after weight fluctuations, pregnancy, or age-related shifts, as ribcage can expand over time.
Why might a calculated size feel off?
Posture during measurement or tape tension affects results. Loose underbust leads to larger bands; over-tight bust shrinks cups unrealistically.
Typical Measuring Errors
Many overlook breathing out for underbust, resulting in oversized bands that slip. Measuring bust over clothing adds false inches, skewing cups larger. Ignoring asymmetry between breasts means one side fits while the other pinches—average the measurements. Rushing without a mirror leads to uneven tape placement, often underestimating by half an inch.
Variations Across Brands
High-street labels like Marks & Spencer stick to traditional UK charts with generous cups for fuller figures. Luxury options from La Perla use slimmer bands for a sleeker profile. Sports brands such as Shock Absorber prioritise compression, sometimes running smaller in cups. Comparing a 34B in Primark might equal a 32C in Freya due to stretch fabrics—always verify brand-specific charts for consistency.
References
Coltman, C. E., Steele, J. R., & McGhee, D. E. (2018). Breast characteristics and bra fit issues in Australian women. Applied Ergonomics, 70, 104-112.
McGhee, D. E., & Steele, J. R. (2010). Optimising breast support in female patients with larger breasts. Journal of Science and Medicine in Sport, 13(5), 507-511.
Brown, S. (2007). The effects of ill-fitting bras on back pain in women. Journal of Chiropractic Medicine, 6(4), 147-152.
Spencer, S., & Brubaker, K. (2013). Factors influencing bra fit and comfort. International Journal of Clothing Science and Technology, 25(6), 442-456.