Chest: A neat measurement around the fullest part of the chest. Breathe normally (since this can affect your measurement) and make sure the tape measure is straight at the back. (GNK TIP: If your chest falls between two sizes, order the size up.
Sleeve: Measure the sleeve of a favourite jacket - from seam to cuff. (And while you’re in there, you may well as check to see if there is a label with a chest size on it too!)