Bra Size Calculator & Guide
Find your perfect bra size with our calculator, measurement guides, and international size conversions
Calculate Your Bra Size
Measure snugly around ribcage under bust
Measure around fullest part of bust
Disclaimer: Bra size calculations are provided as-is for reference only. Sizing varies between brands and styles. Always try bras on when possible.
How to Measure Yourself
1. Underbust Measurement
Measure snugly around your ribcage directly under your bust.
- Exhale normally while measuring
- Keep tape measure parallel to the ground
- Tape should be snug but not uncomfortably tight
- This determines your band size
2. Bust Measurement
Measure around the fullest part of your bust.
- Wear a non-padded bra for accuracy
- Keep tape measure parallel to the ground
- Don't pull the tape too tight
- The difference from underbust determines cup size
Pro Tip: Measure yourself multiple times to ensure accuracy. Most people are wearing the wrong bra size!
Bra Size Conversion Charts
International bra sizes can vary significantly between regions. Use these charts to convert between US, UK, EU, and other sizing systems.
| US | UK | EU | AU | FR |
|---|---|---|---|---|
| 28AA | 28AA | 60AA | 6AA | 75AA |
| 28A | 28A | 60A | 6A | 75A |
| 30AA | 30AA | 65AA | 8AA | 80AA |
| 30A | 30A | 65A | 8A | 80A |
| 30B | 30B | 65B | 8B | 80B |
| 32AA | 32AA | 70AA | 10AA | 85AA |
| 32A | 32A | 70A | 10A | 85A |
| 32B | 32B | 70B | 10B | 85B |
| 32C | 32C | 70C | 10C | 85C |
| 32D | 32D | 70D | 10D | 85D |
| 34A | 34A | 75A | 12A | 90A |
| 34B | 34B | 75B | 12B | 90B |
| 34C | 34C | 75C | 12C | 90C |
| 34D | 34D | 75D | 12D | 90D |
| 34DD | 34DD | 75E | 12DD | 90E |
Note: These conversions are approximate. Always try on bras when possible, as sizing can vary between brands and styles.
Understanding Sister Sizes
Sister sizes are bra sizes that have the same cup volume but different band sizes. They're useful when you need to adjust the fit while maintaining cup capacity.
Going Up a Band Size
If your band feels too tight, go up one band size and down one cup size.
34C → 36B
Going Down a Band Size
If your band feels too loose, go down one band size and up one cup size.
34C → 32D
Common Sister Size Chains
30D
32C
34B
32DD
34D
36C
34DDD
36DD
38D
36DDD
38DD
40D
When to Try Sister Sizes: If the cups fit perfectly but the band is too tight or loose, sister sizes can help you find a better fit without changing cup volume.
Fit Troubleshooting
Even with the right size, bras can fit differently. Here are common issues and solutions:
Cup Gapping
Problem: Fabric doesn't sit flat against your bust, creating gaps or wrinkles in the cup.
Solutions:
- Try a smaller cup size (go from D to C)
- Try a different style - molded cups may not suit your shape
- Check if straps are too tight - loosen them
- Consider a demi-cup or balconette style
Cup Spillage (Quad Boob)
Problem: Breast tissue spills over the top or sides of the cups.
Solutions:
- Go up a cup size (from C to D)
- Try a full-coverage style
- Check if you're scooping all breast tissue into cups
- Consider a sister size with larger cup
Band Rides Up Back
Problem: The back band rides up higher than the front band.
Solutions:
- Try a smaller band size (34 to 32)
- Tighten the hooks - use tighter setting
- Adjust straps - they may be too tight
- Band should be parallel to ground all around
Band Digging In
Problem: Band feels too tight, digs into skin, or leaves marks.
Solutions:
- Try a larger band size (32 to 34)
- Use a looser hook setting
- Consider a sister size with larger band
- Try a different style with wider band
Straps Falling Down
Problem: Straps slip off shoulders constantly.
Solutions:
- Tighten the straps
- Try a bra with closer-set straps
- Consider a racerback or convertible style
- Check if band is too loose (most support comes from band)
Underwire Uncomfortable
Problem: Underwire pokes, sits on breast tissue, or is uncomfortable.
Solutions:
- Try a larger cup size - wire may be sitting on tissue
- Scoop breast tissue fully into cups
- Consider a wireless or soft-cup bra
- Check that underwire follows your natural breast root
Perfect Fit Checklist: Band should be snug and parallel to ground. Cups should contain all breast tissue with no spillage or gapping. Center gore (between cups) should lie flat against chest. Straps should stay in place without digging in.
How to Measure for Bra Size
Measure snugly but not tight - tape should be level all around
Wear your best-fitting bra (non-padded for accuracy)
Stand straight with arms at your sides, relax shoulders
Measure band size: Wrap tape snugly around ribcage directly under bust (parallel to floor)
Measure bust size: Wrap tape around the fullest part of your bust (usually over nipples)
Calculate cup size: Subtract band from bust measurement. Each inch difference = 1 cup size
Cup Size Guide:
- 1" difference = A cup
- 2" difference = B cup
- 3" difference = C cup
- 4" difference = D cup
- 5" difference = DD/E cup
💡 Pro Tip: If band measurement is odd, round up to nearest even number. Tape should be snug but not compressing.
Frequently Asked Questions
How do I measure my bra size accurately?
Measure your underbust (directly under your breasts) and bust (at the fullest part). The difference determines your cup size. Always measure while wearing a non-padded bra and use a soft measuring tape.
What are sister sizes?
Sister sizes have the same cup volume but different band sizes. For example, 34C and 36B are sister sizes. Going up a band size requires going down a cup size to maintain the same fit.
How often should I get measured for a bra?
We recommend getting measured every 6-12 months, or whenever you experience weight changes, pregnancy, or notice your current bras don't fit well. Bra sizes can change throughout your life.
Do bra sizes differ between countries?
Yes! US, UK, EU, and other regions use different sizing systems. Our calculator converts between all major sizing systems. Always check the brand's origin when shopping online.
Why doesn't my measured size feel comfortable?
Bra fit can vary significantly by brand, style, and construction. Use our measurement as a starting point, then try sister sizes and different brands to find your perfect fit. A professional fitting can also help.
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