T-Shirts:

Womens (in inches)
XS: bust 30-32
S: bust 32-34
M: bust 34 –36
L: bust 36-38
XL: bust 38-40
XXL: bust 40–44

Men (in inches)
S: 38–40
M: 42-44
L: 44 – 46
XL: 46-48
XXL: 48-50
XXXL: 50-52