Bra Size Calculator
Free Bra Size Calculator for health & fitness. Enter your measurements for personalized results with clear explanations and reference ranges.
Medical disclaimer: This calculator is provided for educational and informational purposes only and does not constitute medical advice, diagnosis, or treatment. Results are general estimates and may not reflect your individual circumstances. Always consult a qualified healthcare professional before making decisions about your health.
Formula
Cup Size = Bust Measurement - Band Measurement
Measure band snugly under bust, measure bust at fullest point. The difference in inches determines cup size (1 inch=A, 2 inches=B, etc.).
Worked Examples
Example 1: Standard Calculation
Problem:Band measure: 30 inches, Bust: 34 inches.
Solution:Band size = 30 (round to even) Difference = 34 - 30 = 4 inches 4 inches = D cup Size: 30D
Result:30D
Example 2: Sister Size Example
Problem:Wearing 34B but band feels loose.
Solution:Current: 34B Band loose → go down in band Sister size down: 32C (Same cup volume, tighter band) Try 32C for better support.
Result:Try 32C
Example 3: Metric Conversion
Problem:Band: 75 cm, Bust: 90 cm.
Solution:Convert to inches: Band: 75 ÷ 2.54 ≈ 29.5 → 30 Bust: 90 ÷ 2.54 ≈ 35.4 Diff = 35 - 30 = 5 inches = DD Size: 30DD (US) or 65E (EU)
Result:30DD / 65E
Frequently Asked Questions
How do I measure my bra size?
Measure band: around ribcage, directly under bust, snugly. Measure bust: around fullest part, loosely. The difference determines cup size. Wear an unpadded bra or no bra.
What are sister sizes?
Sister sizes have the same cup volume but different band sizes. 34C = 32D = 36B in cup volume. If band is too tight, try sister size up; if too loose, try sister size down.
Why doesn't my calculated size feel right?
Sizing varies by brand. Breast shape, spacing, and fullness affect fit beyond size. Try your calculated size plus sister sizes. Consider professional fitting for best results.
What's the difference between US and UK sizes?
US and UK band sizes are the same (in inches). Cup progression differs after D: US uses DD, DDD, G while UK uses DD, E, F, FF, G. Always check brand's size chart.
How should a properly fitting bra feel?
Band: snug, parallel to floor, 2 fingers fit underneath. Cups: no spillage or gaping. Straps: supportive but not digging. Center: sits flat against sternum.
Why do I get different sizes at different stores?
There's no universal sizing standard. Each brand uses slightly different measurements. Always try on and check the brand's specific size guide.
What is band size?
Band size is the circumference of your ribcage just below the bust, measured in inches (US/UK) or centimeters (EU). It should be snug for support.
How is cup size determined?
Cup size = bust measurement - band measurement. Each inch of difference is roughly one cup size: 1"=A, 2"=B, 3"=C, 4"=D, 5"=DD, etc.
What if I'm between sizes?
Try both sizes. For band, round to nearest even number. For cup, try both adjacent sizes. Consider sister sizes. Fit varies by bra style (t-shirt, sports, etc.).