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Bra Size Calculator

Estimate estimated bra size from bust, band, band size with the Bra Size Calculator.

Choose a bra workflowEstimate a cup index or convert band and cup sizing across regions.
2 options
ESTIMATED BRA SIZE34D

Band 34; bust-minus-band difference 4.0; cup sequences vary by brand.

Estimate based on the values shown
MethodCup index is bust minus band; regional bands convert through centimeters.

Before you use the result

Check the entered units and assumptions before using the result for purchasing, construction, engineering, or safety decisions.

CALCULATOR GUIDE

How to use the Bra Size Calculator

Estimate estimated bra size from bust, band, band size with the Bra Size Calculator. It includes Bra Size, Bra Size Converter workflows, so choose the one that matches the values you actually know. Use it to check a practical estimate, paying close attention to the selected units and assumptions.

Step by step

  1. For the Bra Size, enter bust, band, band size, cup index, region. Keep each value in the unit displayed beside its field.
  2. Review the selected Bra Size workflow and inputs, then read estimated bra size in the result panel.
  3. Change one Bra Size assumption at a time to compare scenarios. Use Reset to restore this tool's worked example values.

How the calculation works

Cup index is bust minus band; regional bands convert through centimeters.

Worked example

In the Bra Size worked example, bust 38 in, band 34 in, band size 34, cup index 4 produces estimated bra size of 34D. Band 34. Review the displayed units before comparing the result.

Understanding the result

The Bra Size reports estimated bra size. Use it to check a practical estimate, paying close attention to the selected units and assumptions. Check the entered units and assumptions before using the result for purchasing, construction, engineering, or safety decisions.

How to check the answer

Check the Bra Size result by reversing the conversion or recomputing estimated bra size from bust, band, band size. For construction, electrical, weather, or purchasing decisions, compare the result with the applicable specification or professional guidance.

Common questions

What does the Bra Size calculate?

Estimate estimated bra size from bust, band, band size with the Bra Size Calculator.

Which Bra Size inputs have the biggest effect?

estimated bra size responds directly to bust, band, band size, cup index, region. Change one input while holding the others constant to see its effect.

Is the Bra Size result exact?

Check the entered units and assumptions before using the result for purchasing, construction, engineering, or safety decisions. Recheck bust, band, band size and use estimated bra size only for a decision where that level of precision is appropriate.

Formula tests, limits, sources, and guide registry updated September 1, 2026.
INTERPRET THE RESULTRead the other guideCheck assumptions, limitations and comparison methods →