Comfort & Confidence

Bra Size Calculator & Converter

Find your exact fitting bra size in US, UK, EU, and AU standards, or convert existing sizes.

Options

Units

Fitting Method

Bust Size

Underbust (Band Size)

Fitting Note: Bra sizes vary by manufacturer. Sizing calculations serve as a guide. Always test sizes with actual fits when shopping.

Fit Guide

How to Measure
For Your Bra Size

Finding the right bra size is essential for comfort and support. Sizing consists of two parts: the Band Size (e.g., 34) and the Cup Size (e.g., B).

Underbust Band

Measure around your ribcage directly beneath your breasts. Keep the tape snug and horizontal.

Overbust Cup

Measure loosely around the fullest part of your chest (across the nipples) to calculate your cup capacity.

Sister Sizes

Understand equivalent cup volumes. Moving down a band size requires moving up one cup size for a similar fit.

Understanding Sizing Standards

Bra sizing varies significantly by country, making international conversions necessary when shopping online:

US/Canada: Standard sizes (28, 30, 32...) use actual band measurements. Cups increase from AA, A, B, C, D, DD, DDD, etc.
United Kingdom (UK): Sized similarly to the US for bands, but uses double letters for larger cups (D, DD, E, F, FF, G, GG...).
Continental Europe (EU): Band sizes are measured in centimeters (60, 65, 70, 75...) and cup intervals are calculated with a standardized 2 cm difference.
Australia/New Zealand (AU): Uses dress sizes for bands (6, 8, 10, 12...) rather than direct measurements.

Fitting Best Practices:

• No Digging: Straps should rest comfortably without leaving deep shoulder indentations.
• Flat Center: The center gore (bridge) must lie completely flat against your breastbone.
• Riding Band: If the back band rides up towards your shoulders, choose a smaller band size.

How the calculation works

The modern method on this calculator rounds the underbust to the nearest even band. The cup is the bust minus that band, rounded to a whole number.

Band = nearest even inch Cup index = round(bust − band) Index 0 is AA, then A, B, C, D, DD/E.

The default inputs are a 38 inch bust and a 34 inch underbust. The traditional method instead adds 4 or 5 inches to the underbust.

Worked example: 38 inch bust and 34 inch underbust

Nearest even band = 34.
Difference = 38 − 34 = 4.
Index 4 is a D cup, so the US size is 34D.

Band from the underbust

Underbust	Even band
34 in	34
31.5 in	32
33 in	34

Frequently asked questions

What size is a 38 inch bust and a 34 inch underbust on the modern method?▼

34D.

How is the band chosen?▼

Round the underbust to the nearest even number. 34 stays 34.

What does the traditional method do instead?▼

It adds 4 inches to an even underbust, or 5 inches to an odd one, and then measures the cup from that larger band.