Bundweite + 15 cm = Gesamtlänge des Gürtels
Waist size + 15 cm = total length of the belt
WAIST SIZE of the belt is NOT the total length of the belt. Measure the part of the body where the belt should sit. You can also measure a belt that fits you up to the buckle and subtract 15 cm. The result is your waist size.
You can also check the size on the inside of the belt that fits you. All belt manufacturers use the same size designation. The mark on the belt is always the WAIST SIZE.