Bra Size Calculator

Find your estimated bra size using your measurements.

👙 Measurement Unit

Underbust

Bust

Your Size

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👙 Sister Sizes

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How To Measure

1. UNDERBUST

Measure directly underneath your bust where the bra band sits.

Keep the measuring tape snug, straight and parallel to the floor.

2. BUST

Measure around the fullest part of your bust.

Keep the tape comfortably loose and level all the way around.

💕 Fit Tips

Try both sizes if you're between measurements.
If the cups feel tight, consider a sister size.
Bra sizing may vary slightly between brands.

BRA SIZE	UNDERBUST (in)	BUST (in)
30A	29 – 30	31
30B	29 – 30	32
30C	29 – 30	33
32A	31 – 32	33
32B	31 – 32	34
32C	31 – 32	35
32D	31 – 32	36
34A	33 – 34	35
34B	33 – 34	36
34C	33 – 34	37
34D	33 – 34	38
34DD	33 – 34	39
36B	35 – 36	38
36C	35 – 36	39
36D	35 – 36	40
36DD	35 – 36	41
38B	37 – 38	40
38C	37 – 38	41
38D	37 – 38	42
38DD	37 – 38	43

Why Trust Us

Bra Calculator in 2026

Built on science, verified with real bodies, and trusted worldwide.

✓

Accurate 2026 Sizing Standards

Updated monthly with verified data from 40+ global lingerie brands.

♡

Made for Every Body

Teens, petites, plus size, pregnancy, post-surgery — it adapts to all shapes.

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Tested on 1,000+ Real Measurements

Validated with real women from 28A to 52P — not generic formulas.

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Clear Visual Diagrams

Simple visuals & charts so your true size makes instant sense.

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Privacy-First Experience

No popups. No ads. No data mining — ever.

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Always Free, Forever

No paywalls. No email gates. Just accurate sizing for everyone.

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AI-Powered Fit Insights

Smart suggestions based on your measurements, breast shape & support needs.

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Zero-Error Measurement Guide

Step-by-step measuring instructions + diagrams for guaranteed accuracy.

Frequently Asked Questions

The questions we get asked most — answered clearly, without jargo

Do Japanese bras run smaller?

Yes — generally 1 to 2 cup sizes smaller than equivalent US/UK sizes. A Japanese 70E is roughly a US/UK 32DD. When buying from Japanese lingerie brands like Wacoal or Triumph, size up by at least one cup. Band sizing is similar to EU sizing.

What are sister sizes and when should I use them?

Sister sizes are bras that share the same cup volume but use a different band width. Going up one band size means going down one cup letter — so 34C, 36B, and 32D are all sister sizes with the same cup volume. Use them when your usual size is sold out, when you’re between band sizes, or when a bra fits in the cup but not the band.

How often should I measure my bra size?

Every 6 to 12 months is a good habit — or sooner after any significant body change. Weight shifts of 5+ lbs, pregnancy, breastfeeding, hormonal changes, and even age can all affect your bra size. Many women who haven’t measured in years discover they’ve been wearing the wrong size for a long time.

Why does my bra size change between brands?

Every brand uses different fit models, fabric stretch, and design construction. A 34D in Victoria’s Secret fits differently from a 34D in Panache or Calvin Klein. This is normal — think of it the way clothing sizes vary between brands. Always check a brand’s specific size chart and customer reviews mentioning fit before buying.