Measure around your under bust and compare it with the cup ranges below.

Brand Size Cup Under Bust (inch)
S 32A/32B/32C/34A 31.0 - 35.0
M 32D/34B/34C/36A 32.5 - 37.0
L 34D/36B/36C/38A 34.5 - 38.5

Natural silk has little stretch. Size up for the best fit.