Bra Size Converter Formula

Understand the math behind the bra size converter. Each variable explained with a worked example.

Use the Bra Size Converter

Formulas Used

EU Band Size

eu_band = (us_band - 32) * 2.54 + 63

UK Band Size

uk_band = us_band

French Band Size

french_band = us_band + 51

Bust Circumference (approx in)

bust_circumference = us_band + us_cup

Variables

VariableDescriptionDefault
us_bandUS Band Size34
us_cupUS Cup (A=1, B=2, C=3, D=4, DD=5)3

How It Works

Bra Size Conversion

Band Size Conversions

| US/UK | EU | French | |---|---|---| | 32 | 70 | 85 | | 34 | 75 | 90 | | 36 | 80 | 95 | | 38 | 85 | 100 |

Cup Sizes

US and UK cup letters generally align through D/DD but diverge at larger sizes. EU uses A, B, C, D, E, F progression.

How to Measure

  • Band: Measure snugly around the ribcage just below the bust
  • Cup: Difference between bust measurement and band measurement (each inch = one cup size)

    • Worked Example

    Convert US 34C to other systems.

    us_band = 34us_cup = 3
    1. 01EU band = (34-32) x 2.54 + 63 = 68 (round to 75)
    2. 02UK band = 34 (same as US)
    3. 03French band = 34 + 51 = 85
    4. 04Cup C is the same letter in US, UK, and EU

    Ready to run the numbers?

    Open Bra Size Converter