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Bra Size Calculator

📅Last updated: October 9, 2025
✓Reviewed by: LumoCalculator Team

Find your bra size from underbust and bust measurements. Supports inches/centimeters with US/UK and EU sizes, sister size guidance, and clear measuring tips.

Bra Size Calculator

Enter your underbust and bust measurements. Supports inches and centimeters.

Your Results

US Size
32DD/E
EU Size
80DD/E
Band / Cup
32 / DD/E

Calculation Method

  • • Band Size: Round underbust to nearest even inch (US/UK) or nearest 5cm (EU)
  • • Cup Size: Bust minus underbust difference mapped to letter (A, B, C...)

Cup Size Reference (Inch Difference)

AA
<0.6"
A
0.6-1.5"
B
1.5-2.5"
C
2.5-3.5"
D
3.5-4.5"
DD/E
4.5-5.5"
DDD/F
5.5-6.5"
G
6.5-7.5"
H
7.5-8.5"
I
8.5-9.5"
J+
9.5+"

How to Calculate

Calculation Formula

1. Band Size = Underbust measurement (rounded to nearest even number)
2. Cup Size = Bust - Underbust difference mapped to letter cup
3. Final Size = Band + Cup (e.g., 34B, 36C)
  1. Accurately measure underbust (snug but not tight)
  2. Measure bust at fullest point
  3. Select measurement unit (inches or centimeters)
  4. View calculated results and size recommendations

Important Considerations

⚠️ Important Notice

Different brands may have varying size standards. We recommend trying on or checking specific brand size charts before purchasing.

Proper Measuring

Stand naturally, use a soft measuring tape horizontally around your body - not too tight or loose

Sister Sizes

Adjacent sizes may also fit, e.g., for 34C try 32D or 36B

Example Cases

Example 1: Standard Measurement

Underbust: 32 inches
Bust: 36 inches
Result: 32D (US/UK)
Sister Sizes: 34C, 30DD

Example 2: Metric Units

Underbust: 75 cm
Bust: 90 cm
Result: 75C (EU)
Equivalent: 34C (US/UK)

Frequently Asked Questions

How do I measure for bra size?
Measure your underbust (snug around the ribcage) and your bust at the fullest point. Keep the tape level and not too tight.
What units are supported?
You can enter either inches or centimeters. The calculator converts and shows sizes for common systems (US/UK and EU).
Are results exact?
Sizing can vary by brand and style. Use this as a starting point, then try adjacent sizes or sister sizes for best fit.
What are sister sizes?
Sister sizes keep cup volume similar while changing band size. For example, 34C ~ 32D ~ 36B depending on band fit.

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