Stand straight with your arm relaxed at your side
Extend the arm you want to measure slightly away from your body
Use a flexible measuring tape
Place the tape at the center of the back of your neck or shoulder point
Run the tape over the shoulder and down the outside of the arm to the wrist bone
Keep the tape straight and snug, not tight
Record the measurement in inches or centimeters
For full arm length, measure from the shoulder point to the tip of the middle finger with the arm fully extended
Measure both arms if you want to compare lengths