11. measure your shoulder to knee length

Start at the point where usually a shoulder seam would meet a collar (just in the middle where your neck 

meets your shoulder), then go down across the fullest part of your chest, straight down to the middle of your 

kneecap.

Make sure the tape measure follows a straight line down. If you are alone, use a mirror, start measuring at the neck point, go down across your chest, hold the measuring tape at the waist and then again at the thigh to be able to read the correct measure at the kneecap.