This style is meant to be oversized, it is not a fitted blouse.
Rae is a size 10-12 on top and wear size S/M in the photos.
Measured flat in CM's
Chest (1cm below armpit) XS67.5 | S/M69 | L/XL72.5
Body Length Front XS65 | S/M66 | L/XL68
Body Length Rear XS70.5 | S/M72 | L/XL75
Rough guide XS 6-8 S/M 10-14 L/XL 16-20
Please note; the guide above is subjective to how you like to wear this blouse.