Measure against your body rather than over your clothing as this will give a more accurate result.

1 Bust:

Measure under the arms at the fullest part around the bust horizontally
2 UNDERBUST:

Measure around your chest, just beneath the breasts ensuring the tape is running straight and level around your body
3 WAIST:

Measure around the natural waistline
4 Hips:

With the feet together measure around the fullest part

SIZE - Inches	BUST	UNDERBUST	WAIST	HIPS
XS	30.5 - 32	25.5 - 27	22.5 - 24	34.5 - 36
S	32.5 - 34	27.5 - 29	24.5 - 26	36.5 - 38
M	34.5 - 36	29.5 - 31	26.5 - 28	38.5 - 40
L	36.5 - 38	33.5 - 33	28.5 - 30	40.5 - 42
XL	38.5 - 39.5	33.5 - 35	32 - 34	42.5 - 44
XXL	40 - 42	35.5 - 37	34 - 36	44.5 - 46