1. Choose a suitable belt or waist ruler and fix it at the waist, paying attention to being close to the skin, which is comfortable and natural.

2. Find the fixing buckle or marking line of the belt or waist ruler, and gently press it on the skin with your fingers, leaving a dent or mark.

3. Take off the belt or waist ruler and measure the length of the marking line with a ruler or ruler to get the waist circumference value.

4. If you want to reduce the waist circumference, you can gradually reduce the length of the belt or waist ruler, not too much at a time. Generally, it is advisable to reduce 1-2 cm each time to avoid physical discomfort or injury.

5. After a period of use and adjustment, re-measure the length of waist circumference to see if the ideal effect has been achieved.