What Is Sizing Like at Nike?

By Ella Blake — Fashion Stylist | Tellar Fashion Hub — Always honest, unbiased & unsponsored

Nike women's sizing generally runs small — particularly in leggings, sports bras, and fitted training tops — and I'd recommend sizing up by one, sometimes even two sizes if you're between sizes or have a curvier build. Their clothing is sized to a US template, which means a Nike medium often fits more like a UK 10–12 rather than the UK 12–14 you might expect.

This is one that's caught me out personally. I remember buying a pair of Nike running tights in my usual size before a half marathon training block — they arrived, I tried them on, and they were so unforgivingly tight around the hips that I genuinely considered returning them. I sized up, the fit was still close (which is what you want for running) but comfortable, and I wore them for about three years solid. The lesson? With Nike, always size up and don't take it personally. It's a sizing quirk, not a reflection of anything else.

The Key Sizing Rule With Nike

Nike uses US sizing as its base, then maps it to UK sizes — and that translation isn't always smooth. Here's the basic principle to keep in mind before you buy anything:

Leggings & tights: Size up one. If you're a UK 12, go for a medium (which Nike maps to UK 12–14). The fabric is compressive by design, but you want movement, not restriction.
Sports bras: Go by your band and cup measurement rather than your clothing size. Nike's sports bra fit is notoriously snug and the sizing varies a lot between styles. Use their bra fit guide before buying.
Running & training tops: Size up if you want any ease of movement. Their fitted styles in particular are cut close — a size small on Nike is closer to a UK 8 than a UK 10.
Oversized and lifestyle styles (e.g. the Phoenix Fleece, hoodies, sweatshirts): These are intentionally oversized — stick to your true UK size or even size down if you want a more structured look rather than full streetwear volume.
Shorts: True to size, generally. Waistband is usually elasticated so more forgiving than fitted bottoms.
Trainers & footwear: True to UK shoe size, though some styles run slightly narrow — worth checking reviews per style if you have a wider foot.

Nike Women's Size Conversion Table

Nike SizeUK SizeEU SizeUS SizeBust (inches)Waist (inches)Hips (inches)XS6–832–342–430.5–3223–24.533–35S8–1036–384–632–3424.5–26.535–37M10–1238–406–834–3626.5–28.537–39L12–1440–428–1036–3828.5–30.539–41XL14–1642–4410–1238–4030.5–32.541–432XL16–1844–4612–1440–4232.5–34.543–45

Nike's Best Lines & How They Actually Fit

Nike has grown into a proper lifestyle brand — it's not just for the gym any more — and different product lines behave very differently in terms of fit. Here's a quick rundown of the ranges most worth knowing about:

Nike Pro (leggings & tights): The original compressive training tight. Fits small — size up one without question. Excellent quality and incredibly durable once you've nailed your size.
Nike Zenvy & Go leggings: The newer, softer feel lines. Slightly more generous in cut than the Pro range — still worth sizing up but not as dramatically so.
Nike Phoenix Fleece: This is the one all over Instagram right now and honestly it lives up to the hype. Intentionally oversized and cropped — wear your true size for the classic look, or size down if you want it less voluminous. A genuinely brilliant piece.
Nike Sportswear (casual/lifestyle): More generous sizing than the performance range — true to size or even size down for a fitted look.
Nike Dri-FIT training tops: Fitted and snug. Size up for comfort, especially if you have a larger bust or broader shoulders.

Nike as a Style Brand — Not Just a Sports Brand

This is worth saying because the conversation around Nike has genuinely shifted. The Phoenix Fleece, the oversized hoodie, the Air Force 1 — these aren't gym pieces any more, they're wardrobe staples. Vogue, Grazia, and every street style photographer have been all over the Nike lifestyle aesthetic for the past couple of years, and I think it's earned. There's a real art to mixing activewear with everyday dressing, and Nike makes it accessible.

My current favourite styling trick: oversized Nike hoodie, straight-leg Levi's, and clean white trainers. Effortless, comfortable, and genuinely looks considered rather than thrown together. Getting the sizing right on the hoodie is crucial though — too big and it tips into shapeless, too small and you lose the whole relaxed point of it.

Brilliant Alternatives to Nike — My Top Picks

Whether you want something at a similar price point, a step up in technical quality, or a slightly different aesthetic, here are my picks for the best Nike alternatives — chosen specifically for their active and lifestyle credentials:

High Street & Accessible Brands

Sweaty Betty — My personal favourite Nike alternative for leggings and training kit. British brand, outstanding quality, sizes that are genuinely consistent and true to UK sizing. Their Zero Gravity leggings are arguably better than anything Nike does at a similar price point.
Lululemon — Premium price but the Align legging is in a class of its own for comfort and fit. Sizing runs small similarly to Nike — size up. Worth every penny for everyday wear.
Gymshark — Hugely popular for good reason. Great for leggings and sports bras, excellent value, and the sizing is consistent once you know your Gymshark size (which tends to run small — same rule applies: size up).
ASOS — Brilliant for activewear dupes and their own-brand active range, plus they stock Nike so you can compare sizing directly. Very useful for trying different brands side by side.
H&M — Their Move range is genuinely underrated for affordable activewear. True to European sizing and much more reliable than you'd expect at the price.
Abercrombie & Fitch — Their YPB (Your Personal Best) activewear line has been brilliantly received. Great for leggings and shorts with a more fashion-forward cut. Sizing is true to standard.
Urban Outfitters — Strong for the lifestyle-sportswear crossover aesthetic. Great hoodies, oversized sweatshirts, and casual active pieces with more personality than the big sports brands.

Premium Picks

Calvin Klein — Their performance and lifestyle active ranges are sleek, minimal, and brilliantly made. A great step up from Nike for the aesthetic-conscious gym-goer. Sizing is true to standard.
Tommy Hilfiger — Their sport and active range has a strong following and the quality is notably above high street. Classic American-sport aesthetic with more structure than Nike.

Two Independent Brands Worth Knowing

Girlfriend Collective — A US-founded but widely available independent activewear brand built on recycled materials and genuinely inclusive sizing (XXS–6XL). Their leggings are consistently praised for their quality and fit, and the sizing is refreshingly true to size. If you've ever found Nike's size range frustrating, Girlfriend Collective is a revelation.
Noli Yoga — A smaller independent brand with a strong cult following among yoga and Pilates communities. Beautiful fabrics, excellent compressive leggings, and a sizing approach that's more generous and body-inclusive than most sports brands. Well worth exploring if Nike's fit just doesn't work for your shape.

🎯 Stop Guessing Your Nike Size — Let Tellar Do It For You

Nike runs small. Lululemon runs small. Gymshark runs small. Activewear sizing is a minefield — and returns are a nightmare when you've just bought three pairs of leggings. Tellar.co.uk is the UK's leading sizing tool, matching your exact measurements to 1,500+ brands instantly so you always order the right size, first time.

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And while you're there, explore the Tellar Fashion Hub — hundreds of honest, unsponsored style posts from our team of stylists. Zero brand deals. Just real advice.