Men's Underwear UK Sizing Guide

Underwear sizing causes more returns than almost any other product category — not because the sizing is complicated, but because it isn't standardised across brands. Here's how to get it right the first time.

The general UK size range

Across our range — Strike Pro, PUMP!, Teamm8, Modus Vivendi and Saligia — sizing runs from SM through XL, occasionally XS or XXL depending on the style. That range maps roughly to:

SM — waist approx. 28–30in / 71–76cm
M — waist approx. 30–32in / 76–81cm
L — waist approx. 32–34in / 81–86cm
XL — waist approx. 34–36in / 86–91cm

Treat these as a starting point, not gospel — always check the size guide on the specific product page. A performance microfibre style and a structured cotton style in the same labelled size will not fit identically.

Why fit varies so much by style

Briefs and boxers are sized primarily off waist measurement, with the amount of stretch in the fabric determining how forgiving that measurement is. Microfibre and modal blends have more give than pure cotton.

Jockstraps add a second fit dimension: the waistband should sit comfortably on the hips while the pouch supports without pinching, and the leg straps need to frame — not dig into — the glutes. Sizing up slightly is common if you're between two sizes, since a jockstrap that's too tight is far more noticeable than one that's slightly loose.

Thongs rely almost entirely on the pouch fit and waistband tension rather than leg coverage, so the size guide is usually the most reliable indicator — there's less fabric overall to compensate for a size that's slightly off.

Fabric changes how "true to size" feels

A cotton style with 0–10% elastane will fit closer to its stated measurement. A microfibre performance fabric, typically an 85% polyamide / 15% elastane blend, has enough stretch that many men comfortably wear their usual size or size down slightly for a more supportive fit. Micro Modal and other modal blends sit in between — soft and slightly stretchy, but not as forgiving as a compression-style microfibre. If you specifically wear PUMP!, our PUMP! true-to-size guide covers that brand's fit in more detail.

What to do if you're between sizes

For everyday briefs, boxers and trunks: size up. Comfort matters more than a snug fit for all-day wear. For jockstraps and thongs, where support depends on the pouch sitting correctly: check the specific product's size guide rather than guessing, since these styles are less forgiving of an incorrect size in either direction.

Still unsure which style to size for? Compare cuts in our briefs vs boxers vs boxer briefs guide, or browse the full range at Men's Underwear UK — every product page carries its own size guide specific to that style and brand.

Related reading

For a broader look at fit and support across the range, see the Men's Bulge Enhancing Underwear Guide.