Women's Bra Size Guide: Understanding Different Bra Size Systems

Many shoppers and importers are confused by women's bra sizes, especially when purchasing products from China or online marketplaces. A bra may be labeled as 40, XL, or 70C / 75B / 80A, even though these represent different sizing systems. This guide explains the most common bra sizing methods in a simple and practical way.

1. Numeric Sizes Only (36, 38, 40, 42...)

Some bras are labeled with numbers only, such as:

  • 36
  • 38
  • 40
  • 42
  • 44

In most cases, these numbers represent the band size (the measurement around the ribcage just below the bust). However, the exact sizing standard may vary by country or manufacturer.

It is important to note that the number alone does not indicate the cup size, so it is not enough to determine the complete bra size.

2. Letter Sizes (S, M, L, XL, XXL)

Some manufacturers use clothing sizes instead of traditional bra measurements, such as:

  • S
  • M
  • L
  • XL
  • XXL

This sizing system is commonly used for:

  • Sports bras
  • Wireless bras
  • Stretch or seamless bras

Although convenient, this system is less precise than the standard band-and-cup sizing system.

3. Standard Bra Sizes (70A, 75B, 80C...)

This is the most accurate and widely used bra sizing system worldwide.

Each size consists of two parts:

  • The number: Band size (underbust measurement in centimeters).
  • The letter: Cup size.

Examples

Size Meaning
70A 70 cm band with a small cup.
75B 75 cm band with a slightly larger cup.
80C 80 cm band with a medium cup.
85D 85 cm band with a large cup.

Cup Size Guide

  • A = Small
  • B = Small to Medium
  • C = Medium
  • D = Large
  • DD or E = Extra Large
  • F = Very Large

What Does C70 / B75 / A80 Mean?

Some suppliers list bra sizes like this:

70C / 75B / 80A

These are known as Sister Sizes.

Sister sizes have approximately the same cup volume while the band size changes.

Size Band Size Cup Volume
70C Smaller Band Larger Cup Letter
75B Medium Band Medium Cup Letter
80A Larger Band Smaller Cup Letter

Although the letter changes, the actual cup volume remains very similar. This is why many manufacturers group these sizes together.

Tips for Importers and Retailers

When sourcing bras from Chinese suppliers, wholesale markets, or platforms such as 1688, Alibaba, and WeChat, never rely solely on the size label.

If a product is labeled only as 40 or XL, ask the supplier whether it refers to:

  • The band size only.
  • A clothing size (S–XXL).
  • A flexible size designed to fit multiple measurements.

Confirming the sizing system before placing an order helps reduce returns, improve customer satisfaction, and avoid costly purchasing mistakes.