Here are some tips to help you order the correct size. If you don't have a tape measure, use a piece of string and hold it next to a ruler.

Raise your arms slightly and measure around your body (without a shirt is best), across the fullest part of your chest.

For casual shirts, find a collared shirt that fits your neck well. Lay the collar flat on a table and measure the "top" edge of the collar. For dress shirts, measure around the base of your own neck, keeping one finger between your neck and the tape measure.

Place your hand on your hip with your arm bent at 90 degrees. Measure from the middle of the back of your neck, across your shoulder and down your arm to your wrist.

Measure around the narrowest part of your abdomen.

Measure around the widest part of your hip.

With your sole flat, measure the distance between your longest toe and your heel.