Reviewed
40B bra size
A 40B has a 40-inch band and a B cup, about 2 inches between band and bust. In the UK it is 40B, in Australia 18B and in Europe 90B.
- US
- 40B
- UK
- 40B
- AU
- 18B
- EU
- 90B
- FR
- 105B
Also fits (sister sizes): 38C firmer band · 42A looser band · all same-volume sizes ↓
40B measurements
- Snug underbust
- 40–41 in · 102–104 cm
- Bust, fullest part
- about 42 in · 105–108 cm
- Cup difference
- 2 in (B cup)
These are starting points from the band-and-cup method. Brands differ by about a size, so a two-minute measurement beats any chart.
40B sister sizes
Same cup volume, different band. If a 40B band feels too loose, go down a band and up a cup; if it feels tight, go up a band and down a cup.
If a 40B doesn't fit
- Band rides up at the back
- Try 38C
- Band digs in, cups fit
- Try 42A
- Spilling over the cups
- Try 40C
- Cups gape or wrinkle
- Try 40A
Not sure what's wrong? Run through the 4-point fit check.
Compare 40B
Sizes next to 40B
40B questions
What is the sister size of 40B?
38C (one band down, one cup up) and 42A (one band up, one cup down). Sister sizes hold the same cup volume on a different band.
What is 40B in UK, Australian and European sizes?
UK 40B, Australia 18B, Europe 90B and France 105B. US and UK cup letters match up to DD and then split.
What measurements are a 40B?
A snug underbust of about 40–41 in (102–104 cm) and a bust of about 42 in (105–108 cm). Measure with the tape level and use the calculator for an exact result.
Is 40B a big size?
40B has a fuller cup volume for a 40 band. Cup letters only mean something next to the band: a 40B holds the same as 28H or 30G.