Using soft measuring tape on bare skin, preferably in the morning before a meal, wrap the tape measure all the way around the waist until the tip overlaps the numbers. (If you don't have a tape measure, use a piece of string and then measure the string with a ruler.)
Be sure that the tape measure is flat against the skin and not twisted. Take a deep inhale and exhale. Do not hold in your stomach or the measurement will be inaccurate. The tape measure should touch your side and back. Your fingers should fit inside the tape measure close to your stomach near your belly button.
Take the measure of the waist to the nearest 0.5 cm (1/4 inch). Enter this double-digit number on the checkout form after you select the gemstones that best align with your intentions.