There are two ways to measure your wrist.
1. Using a soft measuring tape, like one you'd use for sewing, is ideal. Wrap the measuring tape snugly around your wrist. Note the number on the measuring tape, and add a 1/4 inch for a snug fit or a 1/2 inch for a looser fit.
2. Take a string wrap it snugly around your wrist. Once you have the string comfortably wrapped around your wrist, mark the point where the end of the string overlaps the other part. You can use a marker or a pen to make a small mark on the string. Carefully remove the string from your wrist and lay it flat on a ruler or a measuring tape. Measure the length from the end of the string to the mark you made. This measurement represents your wrist size. Add a 1/4 inch for a snug fit 1/2 inch for a looser fit.