Belt Size Calculator (from trouser waist size, inches & cm)

Understanding the belt size calculator — concept and principle

This calculator converts your trouser waist size, or the length of a belt that fits, into the belt size to buy, in inches and centimetres, with the nearest even size and a letter size. It saves guesswork when buying belts online.

Waist + 2 inches: with the default inputs the result is 34 in (≈ 87 cm · size M).

How it is calculated

Belt size (in) = trouser waist (in) + allowance (2 in for regular trousers; more for jeans or low-rise)

Centimetres = inches × 2.54, rounded up

If you measure a belt you own, its length from the fold at the buckle to the middle hole is the size.

The principle

A belt goes round your trousers and shirt as well as your body, so it is labelled a little longer than the trouser waist. Belts worn lower on the hips need a bit more. The labelled size is measured to the middle hole, so a correctly sized belt leaves holes on either side for adjustment. Rounding up is safer because a slightly long belt can be fastened, while a short one cannot.

Worked example

Default inputs: trouser waist 32 in, regular trousers (+2 in).

Belt size = 32 + 2 = 34 in.
In centimetres = 34 × 2.54 = 86.4 → 87 cm.
Next even size = 34 in; letter size M (belt 34–36 in).

How to read the result

Choose the size shown; if between sizes, go up. Sizing tables differ between brands, so check the maker's chart, and remember that some brands label belts by trouser size rather than belt length.

Common mistakes

Buying a belt in your trouser size, which is usually too short.
Measuring your body instead of your trousers or an existing belt.
Measuring a belt to its end instead of the middle hole.

Keep in mind: Brand sizing varies. Check the seller's size guide before buying.

Frequently asked questions

What belt size for 34-inch trousers?

Usually 36 in.

How do I measure a belt?

From where the leather folds at the buckle to the hole you use most.

Are belt sizes the same in Europe?

Many European brands use centimetres, often the belt length to the middle hole.

Sources: Dents, "Belts size guide" (add 2 in to the trouser size) · NIST Special Publication 811 (1 in = 2.54 cm)

Checked 9 Nov 2026. Dents (glove and accessories maker), “Belts size guide” (add 2 in to the trouser size; 3–4 in more for jeans or low-rise trousers; wear the belt on the middle hole; S–XXXL size table); 1 in = 2.54 cm exactly (NIST SP 811, Appendix B).

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