Men's Underwear Size Converter
Find your underwear size from your waist measurement — boxers, briefs, boxer briefs, and trunks. US, UK, and EU sizing.
Full men's underwear size chart
| Waist (in) | Waist (cm) | US | UK | EU | Letter |
|---|
Boxers vs briefs vs boxer briefs vs trunks
Boxers (loose-fit)
Roomy leg openings, no support, often patterned. Best for sleep and lounging. Size matches your waist exactly — if your waist is 32, get size 32.
Briefs (Y-front / classic tighty-whities)
High-cut leg openings, full support, no leg coverage. Best for active wear under athletic shorts. Size by waist; runs true to size.
Boxer briefs
The most popular cut today. Mid-thigh leg, supportive pouch. Calvin Klein, Tommy John, MeUndies popularized them. Size matches your waist.
Trunks
Like a shorter boxer brief — leg ends mid-upper-thigh. Best under slim-fit pants. Same waist sizing.
Brand notes — do men's underwear brands run true?
True to size
Hanes, Fruit of the Loom, Jockey, Calvin Klein, Tommy Hilfiger, Saxx — buy your waist size.
Runs small (size up 1)
Tommy John, ExOfficio, Uniqlo — designed snug. If between sizes, go up.
Runs large (size down 1)
Champion, Russell Athletic — generous American cut. If you like a snug fit, size down.
Special note: international brands
European brands (Hugo Boss, Diesel, Sloggi) tend to use EU sizing where 32" waist = EU 5 or size 5. Always check the chart on the brand's page.
Popular men's underwear picks on Amazon
Best-selling, true-to-size underwear by category.
Frequently asked questions
I don't know my waist size — how do I measure?
Wrap a soft tape around your natural waist (just above your belly button, where your body bends sideways). Don't suck in. The tape should sit snugly but not tight.
What's the difference between waist size and pants size?
Pants size is measured at the hip (lower than waist), so it's usually 1–2 inches BIGGER than your actual waist. Underwear is measured at your true waist. If you wear size 32 pants, your underwear waist size is probably 30 or 31.
Why don't underwear sizes use numbers like pants?
Some brands do (Calvin Klein lists 30, 32, 34 instead of S/M/L), but most use letters because underwear has more stretch — one "M" fits a range (typically 32–34" waist).
What if I'm between sizes?
For briefs and snug boxer briefs: size up for comfort. For boxers (loose-fit) and trunks: size down for a better fit. Watch waistband elastic — too loose rolls; too tight digs in.
How often should I replace underwear?
Underwear should be replaced every 6–12 months for hygiene + elastic break-down. Sooner if waistband elastic is loose, fabric is pilling, or cotton has yellowed.