How to Find Your Perfect Fit at Adidas

By Ella Blake | Tellar Fashion Hub - Honest, unbiased, Unsponsored

Adidas sizing can be genuinely confusing — the brand spans everything from high-performance running gear to oversized streetwear, and each range fits completely differently. Here's everything you need to know to get it right first time.

Adidas is one of those brands I absolutely love in theory but have had more than a few sizing disasters with in practice. I once ordered a pair of Adidas Leggings in my usual size and ended up with something that could generously be described as a second skin. Not a great look for a Tuesday morning run. The issue? I'd picked from the Techfit Performance range without realising it runs a full size smaller than the Originals lifestyle pieces. Lesson learned — and one I'm passing straight on to you.

The short answer is this: Adidas does not have a single universal size chart. The brand's sizing varies significantly depending on the product line, the type of fit, and even the year of manufacture. But once you understand how their ranges are structured, it all starts to make a lot more sense.

Understanding Adidas Sizing: The Basics

Adidas generally sizes in UK/EU sizing, and for most womenswear, their sizes align reasonably closely to standard UK sizing — but with important exceptions. Here's the broad picture:

Performance / Training ranges (e.g. Techfit, Tiro, HIIT gear): These tend to run small and are cut close to the body. If you're between sizes, size up.
Running ranges (e.g. Own the Run, Adizero): Generally true to size, but the waistbands can be snug. Check the inseam length carefully if you're petite or tall.
Adidas Originals (e.g. Trefoil tees, joggers, classic tracksuits): These run large and are designed with a relaxed, streetwear fit. You can comfortably size down here.
Lifestyle / Collaborations (e.g. Stella McCartney, Y-3): Highly variable — always check the specific size guide for these collections as they often use designer-influenced sizing.

The Golden Rule: Always Measure First

I know, I know — measuring yourself feels like homework. But with Adidas, it genuinely makes the difference between a brilliant purchase and an expensive return. The three measurements you need are:

Bust — measured at the fullest point
Waist — your natural waist (usually an inch or so above your belly button)
Hips — measured at the widest point

For bottoms like leggings and shorts, the hip measurement is your most important number. Adidas sportswear is generally designed with a longer torso and narrower hip in mind — if you're curvaceous or pear-shaped, this is where you'll most often need to size up.

Stylist Tip: If you're buying Adidas trainers alongside clothing, note that their footwear tends to run half a size large on women's styles. Many women find sizing down half a size gives a better fit — worth factoring in before checkout.

Adidas vs Other Sportswear Brands: How Does the Sizing Compare?

Context is everything when shopping sportswear. Here's how Adidas sizes up (pun intended) against some of the brands you might already have in your wardrobe:

Sweaty Betty — Runs slightly smaller than Adidas. If you're a medium in Adidas performance gear, you might prefer a large in Sweaty Betty's Power Leggings for the same level of coverage and comfort.
Lululemon — Very consistent sizing, generally true to size, and often more accommodating in the hip area than Adidas performance pieces. Worth knowing if you're curvy.
Gymshark — Runs small, particularly in the waist. Their Vital Seamless range especially — always check reviews before ordering.
ASOS — Their own-brand activewear sizes quite generously, making it a good option for mixing and matching with Adidas pieces where sizing feels tight.
H&M Sport — Tends to run large, similar to Adidas Originals. Good budget-friendly option if you want a relaxed sporty aesthetic.
M&S — Their activewear is excellent for a more traditional UK size — very true to size across the board, and great if you find Adidas performance ranges too snug.
Next — Solidly true to size and includes a good petite and tall range, which Adidas's main line still lacks.

Two Independent Brands Worth Knowing

While we're on the subject of sportswear sizing, two independent brands I've been genuinely impressed by lately are worth a mention:

Girlfriend Collective — An ethical activewear brand that sizes inclusively from XXS to 6XL. Their sizing is refreshingly consistent, their leggings are made from recycled materials, and unlike Adidas performance gear, they genuinely accommodate a range of body shapes without requiring a sizing gamble. A real find.
Varley — A British-founded activewear brand with beautifully cut pieces that sit at the premium end without the designer price tag. Their sizing tends to be generous and the quality is exceptional. If you want the elevated sportswear look with more reliable sizing than Adidas collaborations, Varley is your answer.

Adidas Plus Size and Extended Sizing

It's worth knowing that Adidas has made real strides in extended sizing over recent years. Many of their core performance lines now go up to a 4X or UK size 28, though availability varies by product. If you shop in extended sizes, always go directly to the Adidas website rather than a third-party retailer — their own site tends to carry the full size range. ASOS is also worth checking, as they stock a wide range of Adidas in sizes not always available on the high street.

Key Tips Summary: Getting Your Adidas Fit Right

Know which product line you're buying from — performance vs Originals vs lifestyle fits very differently
If buying performance gear, size up if you're between sizes — especially for leggings and fitted shorts
If buying Originals (joggers, classic tracksuits, hoodies), you can comfortably size down
Always check your hip measurement when buying bottoms
For trainers, consider going half a size down from your usual
Check customer reviews before ordering — they're often more accurate than the size chart alone

Never Guess Your Size Again — Use Tellar

If all this sounds like a lot to remember, there's a much easier way. Tellar.co.uk is the UK's leading free clothing sizing tool, and it takes all the guesswork out of shopping — whether you're buying Adidas, or any of the 1,500+ brands in their database.

Here's how it works:

Measure once — enter your bust, waist, and hip measurements (or just use a brand size you already know fits you well)
Use the Store Size Lookup tool to instantly find your size in any brand — from Adidas to Zara to Reiss
Always free — no sign-up, no downloads, works in-browser

It's genuinely brilliant for sportswear shopping, where sizing inconsistency between brands is the norm. And it's completely independent — no sponsorships, no affiliate bias, just accurate sizing information.

While you're there, explore the Tellar Fashion Hub — a free library of honest, unbiased style guides written by real stylists. Some posts worth checking out:

No ads. No sponsorship. Just good, free fashion advice.