knowhersize

Reviewed

38C vs 40C

40C is bigger than 38C. The cup letter is the same, but cup volume grows with the band, so 40C's cups hold more as well as having the longer band.

Side by side

38C40C
RelationshipSame cup letter, different band
UK38C40C
AU16C18C
EU85C90C
FR100C105C
Underbust38–39 in40–41 in
Bust≈ 41 in≈ 43 in
Cup volume40C holds more

On the size chart

38C is marked in ink and 40C is outlined. The yellow diagonal through 38C shows every size with the same cup volume.

38C = UK 38C · AU 16C · EU 85C · FR 100C. Sister sizes: 36D, 40B. 38C in full →
A
B
C
D
DD
DDD
G
H
28
30
32
34
36
38
40
42
44

Questions

Is 38C or 40C bigger?

40C is bigger than 38C. The cup letter is the same, but cup volume grows with the band, so 40C's cups hold more as well as having the longer band.

Can I wear 40C if I'm a 38C?

Only if the fit check says so. Changing the band also changes the cup volume, so try both where returns are easy.

What are 38C and 40C in UK sizes?

38C is UK 38C and 40C is UK 40C. In Europe they are 85C and 90C.