What this calculator does
Belt size is the waist measurement plus two inches, which is the standard allowance for the buckle and the overlap past it. A 34 inch waist takes a 36 inch belt.
The measurement to use is your actual waist where the belt sits, not your trouser size. Trouser sizing is inconsistent between makers and often flatters, so a pair labelled 34 can measure anything from 34 to 37 at the waistband. Measuring is the only reliable route.
The formula
Two inches are added to the waist measurement and the result rounded to the nearest even number, since belts are almost always sold in even sizes. The centimetre conversion is provided because European belts are sized in centimetres and use the same underlying measurement.
| Term | Meaning |
|---|---|
| Belt size | Measured from the buckle fold to the middle hole, not the overall length of the strap. |
| Two inch allowance | The standard addition for the buckle and overlap. |
| Middle hole | Where a correctly sized belt should fasten, leaving holes either side for adjustment. |
The inputs explained
| Field | What to enter |
|---|---|
| Waist measurement (pant size or tape reading) (in) | Waist measurement in inches, taken where the belt actually sits rather than at the narrowest point. |
When to use it
Buying a belt online
Without trying it on, the measurement plus two inches is the reliable route, and it beats guessing from trouser size.
Buying a belt as a gift
Their trouser size is easier to discover than their waist, but it is a worse guide. Measuring an existing belt they wear is better still.
Checking a European size
European belts are marked in centimetres, and the conversion turns the recommendation into the number on the label.
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
What belt size does each waist need?
A range of waist measurements with the recommended belt size.
| Waist measurement | Recommended belt size | In centimetres | Rule used |
|---|---|---|---|
| 30 in | 32 in | 81 cm | Belt size = waist measurement + 2 in, rounded up to the nearest size sold (belts are usually sized in 2 in steps) |
| 34 in | 36 in | 91 cm | Belt size = waist measurement + 2 in, rounded up to the nearest size sold (belts are usually sized in 2 in steps) |
| 38 in | 40 in | 102 cm | Belt size = waist measurement + 2 in, rounded up to the nearest size sold (belts are usually sized in 2 in steps) |
| 42 in | 44 in | 112 cm | Belt size = waist measurement + 2 in, rounded up to the nearest size sold (belts are usually sized in 2 in steps) |
Questions
How is belt size measured?
From the fold at the buckle to the middle hole, not the total length of the strap. This is why a belt marked 36 is physically longer than 36 inches: the tail past the middle hole and the buckle itself are extra.
Should I use my trouser size?
Not if you can measure instead. Trouser waist labels are inconsistent between makers and frequently run larger than marked. Measuring where the belt actually sits gives a figure that does not depend on anyone sizing conventions.
What if I am between sizes?
Size up. Belts are sold in even sizes so an odd measurement always falls between two, and the larger one simply fastens on an inner hole. The smaller one may not reach at all.
Does it differ for a dress belt and a jeans belt?
Slightly. A dress belt sits at the natural waist and a jeans belt lower on the hips, and those two measurements can differ by an inch or two on the same person. Measure at the position the belt will actually be worn.
For other sizing conversions, see the shoe size converter and the hat size calculator.