Your waist is the number most people give when asked for a size, and the number on a pair of trousers, a belt or an elastic waistband. This calculator takes the waist measurement and returns the trouser size in letters and numbers for women and men, and a belt size for men, from published charts.
How to use the waist size calculator
- Choose women’s or men’s sizing.
- Measure around the narrowest part of the torso with the tape horizontal. For trouser sizing you can also measure where the waistband sits.
- Enter the number in inches or centimetres.
- Read the result: the letter size, number size and, for men, the belt size.
Waist size formula (chart lookup)
belt size = trouser size + 2 in
hips and waist differ → follow the hips (Nike)
The charts are Nike’s bottoms charts, which list body measurements (retrieved 2026-10-15), and the belt rule is from Proper Cloth’s belt guide. Nike’s own belt chart lists belt sizes 30–32 for pants 28–30 (lifestyle belts), which agrees with adding two inches.
| Women | Waist (in) | Waist (cm) |
|---|---|---|
| XXS | 21.25 – 23.5 | 54 – 60 |
| XS | 23.5 – 26 | 60 – 66 |
| S | 26 – 29 | 66 – 74 |
| M | 29 – 31.5 | 74 – 80 |
| L | 31.5 – 34.5 | 80 – 88 |
| XL | 34.5 – 38.5 | 88 – 98 |
| XXL | 38.5 – 42.5 | 98 – 108 |
| Men | Waist (in) | Waist (cm) |
|---|---|---|
| XXS | 22.5 – 25.5 | 57 – 65 |
| XS | 25.5 – 29 | 65 – 74 |
| S | 29 – 32 | 74 – 81 |
| M | 32 – 35 | 81 – 89 |
| L | 35 – 38 | 89 – 97 |
| XL | 38 – 43 | 97 – 109 |
| XXL | 43 – 47.5 | 109 – 121 |
| 3XL | 47.5 – 52.5 | 121 – 133 |
| 4XL | 52.5 – 57 | 133 – 145 |
Worked example
A man with a 33 inch waist.
- Letter: 33 is within 32–35 → M (waist 32–35 in).
- Numeric size: Nike’s size 32 is made for a 33.5 inch body waist, so the trouser label is 32.
- Belt: 32 + 2 = 34.
Waist measuring tips
- Natural waist: bend sideways; the crease that forms is the natural waist.
- Time of day: measure before a big meal, as waists vary through the day.
- Breathing: relax and breathe out, and do not pull in your stomach.
- Different brands label waist sizes differently, so check a brand’s own chart too.
For belts see the Belt Size Calculator; for hips the Hip Size Calculator; for denim the Jeans Size Calculator. This page is general sizing guidance.
Sources
Every figure above comes from these pages, read directly on the dates shown. Brand names are used only to identify published charts.
- Nike — men’s bottoms size chart (waist) — checked 2026-10-15
- Nike — men’s numeric bottoms chart (waist, hip) — checked 2026-10-15
- Nike — women’s bottoms size chart — checked 2026-10-15
- Nike — women’s numeric size chart — checked 2026-10-15
- Nike — belt size chart (belt size vs pant size) — checked 2026-10-15
- Proper Cloth — how to measure belt size (pant size + 2) — checked 2026-10-15
Frequently asked questions
How do I measure my waist?
Measure around the narrowest part of the torso, which is typically where the body bends side to side, keeping the tape horizontal, as Nike describes it. Wikipedia-based charts for trousers use the waist where you wear your pants, which sits lower, so the two numbers can differ by an inch or two.
How does waist convert to trouser size?
Nike’s charts list the body waist for each size, and the label is smaller than the body waist for men: a size 32 corresponds to a 33.5 inch body waist. The calculator finds the first size whose body waist is at least yours.
What belt size do I need?
Proper Cloth’s rule is to add 2 inches to your trouser size, so a size 34 needs a 36 belt (3 or 4 inches for low-rise). The calculator adds 2 to the trouser label. See the Belt Size Calculator for more.
Waist or hips: which decides?
Nike says to order the size indicated by the hips when waist and hips point to different sizes. Use the Hip Size Calculator to check.
Is waist size the same as natural waist?
Not always. The natural waist is the narrowest part; many people wear trousers on the hips, where the circumference is larger. Measure where the waistband will sit if you want a more accurate fit.