1. Measure the relevant parts of your body as per the instructions below.
2. Use those measurements against the appropriate size guide shown in the list here.
3. Select the size that is closest to, but not below your measurement.
Measure yourself standing upright but relaxed. Keep the measuring tape firm, but not tight. Try to take your measurements more than once, to average out any changes in your posture.
Measuring your chest
Measure around the fullest part of your chest, keeping the tape level under your arms and across your back.
Measuring your waist
Easy – just measure around the narrowest part of your waistline – usually it's just above your belly button.
Measuring your collar
Measure round the fullest part of your neck and add half an inch.
Measuring your inside leg
Take the measurement from the very top of your inside leg, down to your ankle bone.
For Men's Footwear sizes, see here.