ganak.appBra Size Calculator
Free bra size calculator. Enter underbust and bust measurements to find your bra size in US, UK, EU, AU & JP systems. Includes sister sizes, international size chart, and step-by-step measurement guide.
Measure your underbust snugly around the ribcage, just below the bust. For the bust, measure at the fullest point while wearing a non-padded bra. Keep the tape level and parallel to the ground.
32D
Your bra size is 32D. If the band feels too tight, try the sister size with a larger band (34C).
Your Size Across Systems
International bra size equivalents for your measurements
US
32D
UK
32D
EU
70D
AU
10D
JP
70D
Sister Sizes
Alternative sizes with the same cup volume — try these if your band feels too tight or loose
Tighter Band
30DD/E
Smaller band
larger cup
Your Size
32D
Best fit
Looser Band
34C
Larger band
smaller cup
Measurements Used
The underbust and bust values used to determine your size
Underbust
32"
Bust
36"
Difference
4"
Bra Size Chart
Quick reference chart — your size is highlighted
| Band | A | B | C | D | DD/E | DDD/F | G | H |
|---|---|---|---|---|---|---|---|---|
| 28 | 28A | 28B | 28C | 28D | 28DD/E | 28DDD/F | 28G | 28H |
| 30 | 30A | 30B | 30C | 30D | 30DD/E | 30DDD/F | 30G | 30H |
| 32 | 32A | 32B | 32C | 32D | 32DD/E | 32DDD/F | 32G | 32H |
| 34 | 34A | 34B | 34C | 34D | 34DD/E | 34DDD/F | 34G | 34H |
| 36 | 36A | 36B | 36C | 36D | 36DD/E | 36DDD/F | 36G | 36H |
| 38 | 38A | 38B | 38C | 38D | 38DD/E | 38DDD/F | 38G | 38H |
| 40 | 40A | 40B | 40C | 40D | 40DD/E | 40DDD/F | 40G | 40H |
| 42 | 42A | 42B | 42C | 42D | 42DD/E | 42DDD/F | 42G | 42H |
| 44 | 44A | 44B | 44C | 44D | 44DD/E | 44DDD/F | 44G | 44H |
| 46 | 46A | 46B | 46C | 46D | 46DD/E | 46DDD/F | 46G | 46H |
| 48 | 48A | 48B | 48C | 48D | 48DD/E | 48DDD/F | 48G | 48H |
How Bra Sizing Works
Understanding the relationship between your measurements and bra size
Bra size consists of two parts: a band number (the circumference around your ribcage) and a cup letter (the volume of the bust relative to the band). The band size comes from your underbust measurement, while the cup size is determined by the difference between your bust and band measurements — each inch of difference corresponds to one cup size.
Different countries use different numbering systems. A US 34D is the same as a UK 34D, EU 75D, AU 12D, and JP 75D. This calculator converts between all major systems automatically.
Band Size
From Underbust
Underbust measurement rounded to nearest even number
Cup Size
Bust − Band
Each inch of difference equals one cup letter
5 Systems
US UK EU AU JP
Automatic conversion across international sizing
How to Measure for Your Bra Size
Step-by-step guide for accurate underbust and bust measurements
1. Underbust (Band)
Wrap the tape around your ribcage, directly under your bust. Pull it snug — firm enough to stay in place but not so tight it digs in. This determines your band size. Exhale normally while measuring.
2. Bust (Cup)
Measure around the fullest part of your bust, typically across the nipple line. Wear a non-padded bra or measure braless. Keep the tape level and gently snug — not compressing.
3. Check Your Posture
Stand upright with arms at your sides. Don't slouch, lean, or lift your arms while measuring. For the bust measurement, lean slightly forward to let your breasts fall naturally for the most accurate reading.
4. Tips for Accuracy
Measure at the same time of day (breasts can fluctuate slightly). Use a mirror to ensure the tape is level in the back. Have someone help if possible. Re-measure if the first reading feels off.
What Are Sister Sizes?
Understanding how band and cup sizes relate to each other
Sister sizes are bra sizes that share the same cup volume but have different band sizes. When you go up one band size, you go down one cup letter — and vice versa. For example, 34C, 32D, and 36B are all sister sizes with the same cup volume.
This is useful when a bra fits in the cup but the band feels too tight or too loose. Instead of changing cup sizes, try a sister size: go up a band for more comfort, or down a band for more support.
Band Too Tight?
Go up one band size and down one cup letter. For example, if 32D feels tight, try 34C — same cup volume, more room in the band.
Band Too Loose?
Go down one band size and up one cup letter. For example, if 36B rides up, try 34C — same cup volume, more snug support.
Common Bra Sizing Mistakes
Avoid these pitfalls when measuring and choosing your bra size
Measuring over a padded bra
Padded bras add 0.5-2 inches to your bust measurement. Always measure in a non-padded bra or braless for accurate results.
Wearing the wrong band size
About 80% of bra support comes from the band, not the straps. If your band rides up in the back, it's too loose. A properly fitting band stays parallel to the ground.
Ignoring cup shape differences
Two bras in the same size can fit differently based on cup shape (full cup, demi, plunge). Your size is a starting point — try different styles to find what works for your shape.
Not re-measuring regularly
Bra size can change due to weight fluctuations, hormonal changes, aging, and exercise. Re-measure every 6-12 months or after any significant body changes.
About the Bra Size Calculator
How bra size calculation works using underbust and bust measurements
This calculator determines your bra size by using your underbust (band) and bust measurements. The band size is calculated by rounding your underbust to the nearest even number (US/UK) or nearest 5cm (EU/JP). The cup size is determined by the difference between your bust and band measurements — each inch (or 2cm for EU) equals one cup letter. Results are shown across five international sizing systems (US, UK, EU, AU, JP) with sister size recommendations. The calculator supports both inches and centimeters for input.
Frequently Asked Questions
Common questions about bra sizes, measurements, and international conversions