Measure at the fullest part of your bust, by placing the tape measure under your arms and across your shoulder blades. Remember to breathe out when taking this measurement.
Decide where you want your trousers to sit (on the hips, above the hips) and measure at this position. Ensure that the tape is horizontal to the ground.
Measure around the fullest part of your bottom, about 20cm below your natural waist, at the top of your legs.