Men’s underwear is one of the easiest garments to size, because the chart is built on one measurement, the waist. Yet comfort depends on getting it right: a waistband that rolls down is too large, and one that digs in is too small. This calculator turns your waist measurement into a size on two published charts, Nike’s underwear size chart and Fruit of the Loom’s men’s underwear guide.
How to use the men’s underwear size calculator
- Measure your waist around where you normally wear your pants, slightly below the natural waist.
- Allow ease: put a forefinger between the tape and your body, as Fruit of the Loom suggests.
- Enter the waist in inches or centimetres.
- Read the sizes. If you are between sizes, the larger size is shown.
Underwear size formula (chart lookup)
between sizes (gaps in the chart) → the next larger size
The waist ranges (in inches) are from the Fruit of the Loom men’s underwear size table and Nike’s underwear chart (retrieved 2026-10-15). Nike’s figures are body measurements. A waist exactly on the upper limit belongs to that size; one in a gap, such as 31 in, belongs to the size above.
| Size | Nike waist (in) | Nike chest (in) | Fruit of the Loom size | Fruit waist (in) |
|---|---|---|---|---|
| XS | 24 – 26 | 30 – 32 | — | — |
| S | 28 – 30 | 34 – 36 | S | 28 – 30 |
| M | 32 – 34 | 38 – 40 | M | 32 – 34 |
| L | 36 – 38 | 42 – 44 | L | 36 – 38 |
| XL | 40 – 42 | 46 – 48 | XL | 40 – 42 |
| XXL | 44 – 46 | 50 – 52 | 2XL | 44 – 46 |
Worked example
A waist of 33 inches.
- It is above Nike’s S (28–30) and within M (32–34), so Nike size M (waist 32–34 in, chest 38–40 in).
- On the Fruit of the Loom chart it is also within M (waist 32–34 in).
- A waist of 31 inches sits in the gap between S and M; both brands tell you to take the larger, M.
Choosing a style
- Boxer briefs: snug through the leg; choose the leg length you prefer, and the waist size is the same.
- Boxers: looser fabric, so a small size error matters less at the leg but still at the waistband.
- Briefs: need a firm fit at the leg openings, and a size down from boxers is common.
- Fabric: cotton shrinks a little; synthetic blends hold their shape.
The calculator gives general guidance from two brands; other makers differ by an inch at the edges, so also check the maker’s size chart. For trousers and belts see the Pants / Trouser Size Calculator and Belt Size Calculator.
Sources
Every figure above comes from these pages, read directly on the dates shown. Brand names are used only to identify published charts.
- Nike — underwear size chart (men’s chest and waist, women’s waist and hip) — checked 2026-10-15
- Fruit of the Loom — men’s underwear size guide (waist, measuring tip, between sizes) — checked 2026-10-15
Frequently asked questions
How do I find my underwear size?
Measure around your waist where you normally wear your pants, with a finger between the tape and your body for ease, as Fruit of the Loom advises, and look up the number. Wearing your underwear while you measure gives a more accurate result.
What if I am between sizes?
Both charts leave gaps, for example Nike’s S is 28–30 and M is 32–34. Fruit of the Loom says to pick the next larger size if your measurement is between the listed sizes, and the calculator does the same.
Is underwear size the same as pants size?
Not exactly. Pants are labelled by a nominal waist that sits low on the hips, and underwear by the body waist. A man in size 34 jeans usually measures a 32 to 34 inch waist and takes an M. See the Pants / Trouser Size Calculator.
Why do Nike and Fruit of the Loom give the same size?
Their waist ranges match: S is 28–30, M is 32–34, L is 36–38, XL is 40–42 and 2XL/XXL is 44–46. Nike’s XS (24–26) has no Fruit equivalent, and Fruit adds a 3XL (48–50).
Do boxers and briefs fit the same?
The waist size is the same but briefs need a good fit at the leg openings and boxers at the seat, so also use the brand’s notes on the style. The Shapewear Size Calculator covers compression styles.