Most mass-produced belts are manufactured in large volumes, often with little emphasis on precision. Hole placement, tip length, and overall proportions vary widely. As a result, the stated belt size rarely reflects how the belt actually fits.

The number stamped on the back of a commercial belt is not a true belt size. In many cases, it is measured from the leather fold and does not account for the buckle length. Even then, there is usually no clear standard behind how that measurement was taken. That number tells us nothing we can reliably work with.

Waist size is also not the same as belt size.

Think about how a belt is actually used. You tighten it slightly every time you wear it so that your trousers stay in place. Depending on how you dress, tuck in clothing, or adjust tension, the belt you wear can be shorter or longer than your actual waist circumference.

Finally, every buckle has its own dimensions. The buckle you choose directly affects the required belt length, and this must be accounted for during construction.