Question 1

What are sister sizes?

Accepted Answer

Sister sizes are bra sizes with the same cup volume but different band-cup combinations. For example, 34C, 32D, and 36B are sister sizes. Going up one band size and down one cup size (or vice versa) maintains the same cup volume while adjusting the band fit.

Question 2

Why doesn't my usual brand match exactly?

Accepted Answer

Bra sizing varies significantly between manufacturers due to differences in materials, construction, and regional standards. Use our converter's results as a starting point, then check each brand's specific size chart and consider trying sister sizes for the best fit.

Question 3

Do you use the +4 rule?

Accepted Answer

We default to a modern nearest-band approach, which many experts now recommend. However, you can toggle to the traditional +4 method (adding 4-5 inches to your underbust measurement) if you prefer that sizing convention.

Question 4

Are UK and US cup sizes identical?

Accepted Answer

UK and US sizing are generally similar, but the UK commonly uses double letters (DD, FF, GG, HH) where US sizing might use single letters or different naming (like DDD instead of E). Our converter handles both styles and lets you toggle between them.

Question 5

How do I measure for the calculator?

Accepted Answer

For underbust: Measure snugly around your ribcage directly under your bust. For bust: Measure around the fullest part of your bust while standing. Keep the tape parallel to the ground and don't pull too tight. Measurements should be taken while wearing an unpadded bra or no bra.

Question 6

Is this medical advice?

Accepted Answer

No. This tool provides informational estimates only and is not a substitute for professional fitting or medical advice. For the most accurate fit, consider getting professionally fitted at a lingerie store.

Question 7

What if my measurements fall between sizes?

Accepted Answer

If you're between sizes, try both and see which feels more comfortable. Also check the sister sizes we provide — they have the same cup volume but different band fits, which might work better for your body shape.

Question 8

Why do some regions skip certain cup letters?

Accepted Answer

Different regions have different naming conventions. For example, US/UK sizing traditionally uses DD instead of E, and may use DDD or F interchangeably. EU and JP sizing typically use single letters without doubles. Our converter normalizes these differences.

Bra Size Converter