Step 1: Measure your wrist just below the wrist bone, where one would normally wear a bracelet, with a flexible measuring tape, or a strip of paper. 

Step 2: If you are using a plain strip of paper, then measure that item with a ruler to determine your wrist size. 

Step 3: Add 1/4 inch to 1 inch to your wrist size, depending on whether you would like a snug, comfort, or loose fit.