What Is Sizing Like at Under Armour?

Under Armour runs true to size.

The big thing nobody explains: three cuts, not three sizes

This is the bit that trips everyone up. Under Armour builds most of its kit in three different fits — and these are cuts, not sizes. You pick your normal size, then you pick the fit for the feel you want.

Compression — second-skin tight, engineered to sit snug against the muscle for support and to wick sweat. It's meant to feel like that. This is the fit that scares people in the changing room.
Fitted — a slimmer, athletic cut that follows the body without squeezing. No excess fabric flapping about, but you can breathe. For most men, this is the sweet spot.
Loose — a fuller, relaxed cut with room to move and better airflow. This is your gym-to-café tee, your layering piece, your recovery-day hoodie.

Once you know which of those three you're holding, the sizing suddenly makes sense.

Does Under Armour run true to size?

Yes — with one asterisk. UA built its gear to sit within traditional sizing, so if you're a genuine Large in a decent tee, you're a Large in a UA Fitted or Loose piece. No drama. The asterisk is Compression: it deliberately runs smaller because it's supposed to. My rule of thumb, refined over years of kitting clients out:

Fitted & Loose: buy your normal size. It'll do exactly what it says.
Compression: buy your normal size if you want the performance effect. Only size up if you genuinely can't stand a tight fit — but know you're trading away the support it's built for.
Between sizes? Size up in Loose, size down (or stay put) in Fitted.

The numbers that actually matter

Tops go by chest, bottoms go by waist and hip — and UA is one of the more honest brands about publishing real ranges. As a reference point, a Medium top covers roughly a 96–102cm (38–40in) chest, and Medium bottoms sit around a 76–81cm (30–32in) waist. Measure yourself once, match the row, and you'll rarely go wrong. It's a world away from the vague "M/L" guesswork you get on a lot of fast-fashion sportswear.

A quick word on the trainers

UA lists its footwear as true to size, but they're cut like proper performance shoes — snug through the midfoot with a close toe box. If you've got wider feet, you sit between sizes, or you train in thick socks, go up a half size. I learned that the hard way on a pair of HOVR runners that were perfect for about three miles and then very much weren't.

What to buy — and what's actually on trend

Under Armour has quietly become more than gym kit. The technical-athleisure crossover is having a real moment, and UA sits right in the middle of it. Here's where I'd spend:

HeatGear base layers — the fitted short-sleeve tees are the workhorse of the range. Breathable, they hold their shape, and they layer beautifully under an overshirt.
A ColdGear half-zip — the single most versatile piece UA makes. Warm, stretchy, and it looks the part with joggers or under a jacket on a cold morning commute.
Loose-fit training shorts with a liner — the compression-liner-under-a-relaxed-short combo is genuinely brilliant for running and HIIT, and it's bang on trend right now.
A relaxed hoodie in a muted tone — skip the loud logos. Slate, olive and stone are where menswear is heading, and they wear far better off-duty.

How to style it without looking like you're about to sprint

The trap with performance wear is looking like you've wandered out of a spin class by accident. The fix is contrast. Pair a fitted UA base layer with a proper cotton overshirt and clean trainers, and it reads as considered, not gym-bound. Keep the technical stuff to one or two pieces per outfit — a half-zip or the joggers, not head-to-toe. And stick to a tight colour palette: neutrals up top, one anchor colour below. Athleisure done well is about restraint, not more zips.

Eight brands I'd put alongside Under Armour

UA is superb at what it does, but a good wardrobe isn't a single-brand affair. Here's who I'd shop across three tiers, and why.

High street

Gymshark — the British name that redefined this whole category. Their fitted training pieces cut slim and modern, and the price is friendly. Just note they run leaner than UA, so size up if you're between.
adidas — unbeatable for the athleisure crossover. The Terrex and originals lines give you technical credibility and street-ready looks, and the sizing is reliably true.
Nike — the obvious one, but earned. Dri-FIT holds up, the fits are consistent, and nothing layers under a coat quite as cleanly as a plain Nike base tee.

Independent & boutique

Castore — a British premium sportswear label doing beautifully understated, logo-light performance kit. If you want to look sharp at the gym without shouting, this is it. Cuts on the trim side.
Iffley Road — proper British running wear made like proper clothing. Merino and technical fabrics, timeless colours, built to outlast three seasons of UA. A quiet luxury take on performance.

Designer & luxury

Y-3 — the adidas × Yohji Yamamoto collaboration, and the gold standard for elevated sportswear. Sizing runs oversized and Japanese-avant-garde, so try before you commit, but nothing else bridges gym and gallery like it.
lululemon — technically athleisure, but the fabric and fit put it in a class of its own. The ABC trousers and Metal Vent tees are worth every penny, and the fits are famously flattering.
On — the Swiss running brand that's become a genuine style label. Immaculate minimalism, premium technical fabrics, and trainers that look as good with trousers as with shorts.

My verdict: Under Armour runs true to size in Fitted and Loose — buy your normal size with confidence. Only Compression runs small, and that's by design. Measure your chest and waist once, decide which of the three cuts you're after, and it's one of the most predictable brands out there.

Never squint at a size guide again

Here's the thing about everything I've just told you — you shouldn't have to memorise it. That's exactly why I send every client to Tellar, the UK's leading sizing tool. Match your body to 1,500+ brands instantly and get your precise size in Under Armour, COS, Reiss, Everlane, Arket and hundreds more — no more guesswork, fewer returns, better-fitting kit.

Measure once — bust, waist, hip, or just tell it a brand size you already know fits.
Look up any store — get your exact size in each brand, including UA's tricky Compression cut.
Shop with confidence — no downloads, works in your browser, always free.

Find My Under Armour Size How to Measure

And when you've sorted your size, dig into the Tellar Fashion Hub — a library of free posts from our stylists covering every fashion question you can think of. Honest. Unbiased. Independent. Always free.