What Size Am I in Certified Sports? The Honest Sizing Guide You Actually Need

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

Certified Sports runs oversized by design — in most cases you should size down by one full size from your usual UK sizing, especially in tops, hoodies, and tracksuits. The brand intentionally builds in a relaxed, boxy, streetwear silhouette, so if you're used to a standard fitted UK 10–12, a Small or XS in Certified Sports is often the better call.

Right, let's get into the detail — because this brand trips people up more than most. I've seen it happen so many times: someone orders a medium thinking it'll be a snug, flattering oversized fit, and it arrives looking like a small tent. Not the look. Certified Sports is brilliant if you understand what it's doing stylistically, but the sizing genuinely doesn't behave like most high street brands. Here's everything you need to know before you buy.

A Bit About the Brand

Certified Sports has made a serious name for itself in the UK streetwear and activewear scene. This is a brand built on heavyweight fabrics, strong graphic branding, and that premium, structured feel — the kind of thing that looks effortlessly cool worn with Nike Air Force 1s and a good pair of wide-leg jeans. Think limited drops, thick cotton, and that "I know what I'm doing" energy. It's popular with women who want their loungewear to feel intentional rather than like gym kit.

The issue is that Certified Sports uses a unisex or male-leaning cut for a lot of its pieces, and it actively leans into the oversized aesthetic. So the size label is essentially a starting point — not a guarantee of what it'll look like on your body.

The Key Thing to Know About Certified Sports Sizing

The brand uses standard UK labels (XS, S, M, L, XL, XXL) but the actual fit runs a full size — sometimes more — larger than expected
Drop-shoulder constructions exaggerate the boxy shape significantly
Thick cottons (often 250–300gsm) and fleece don't stretch or "give" the way jersey fabrics do
Cuts are designed to look intentionally relaxed, not just generously cut
Sizing isn't always consistent between collections — always check measurements before buying a new style

💡 Ella's tip: If you already wear Corteiz, Trapstar, or Hoodrich, Certified Sports typically runs larger than those brands — particularly in the chest and shoulders. A Medium in Corteiz often feels like a Large in Certified.

Certified Sports Women's Size Conversion Guide

Label SizeUK Dress SizeChest (cm)Waist (cm)Fit NoteXS6–884–8870–74Slim / petite frame; still relaxedS8–1089–9375–79Good pick if you want close-ish oversizedM10–1294–9980–85Best-selling size; genuinely roomyL12–14100–10586–91Designed to sit loose — very boxyXL14–16106–11192–97Drop shoulder is very exaggeratedXXL16–18112–11898–104Pure oversized statement piece territory

How Each Garment Fits

T-Shirts

The tees are thick — we're talking structured cotton that holds its shape. The drop shoulder creates a wider look across the upper body and the hem sits low. On a standard UK 10–12, a Small gives a flattering oversized finish without drowning your frame. A Medium starts to look genuinely large on smaller builds.

👕 Sizing advice: Size down one from your usual. A UK 10–12 → Small. A UK 14 → Medium.

Hoodies

These are Certified Sports' signature piece and where the sizing mismatch is most felt. The ribbed hem grips slightly at the waist but the body and arms stay very roomy. The fleece is thick and doesn't drape — it sits away from the body. If you want that cool, slightly-too-big-but-intentional look, go true to size. If you want it fitted and cosy, size down.

🧥 Sizing advice: Go true to size for the streetwear aesthetic. Size down one for a more fitted silhouette.

Tracksuits & Joggers

The joggers are actually one of the more accommodating pieces — tapered from the thigh to the ankle and relatively true to size through the waist. If you've got curvier hips, you might want to size up and use the drawstring to adjust the waist. The taper is flattering; these are not a problematic fit in the way the tops can be.

👖 Sizing advice: Go true to size or consider sizing up if you're fuller in the hip/thigh. The tapered ankle keeps them looking streamlined.

Outerwear & Coats

Structured and minimal stretch. Certified's padded and cropped jackets are cut closer to size than the rest of the range — but always check the chest and shoulder measurements before buying, especially online. These pieces can look brilliant if the shoulder seam sits in the right place.

🧤 Sizing advice: Stick to true size. Focus on chest and shoulder measurements — use Tellar's Store Size Lookup to confirm before ordering.

Similar Brands That Are Easier to Size

If you love the Certified Sports aesthetic but want something easier to size — or you want to build a comparable wardrobe around it — here are some brilliant alternatives:

High Street Picks

ASOS — their own-brand oversized hoodies and streetwear drops are consistently sized and excellent value; the size filter makes it easy to shop confidently
Zara — brilliant for structured sweatshirts and co-ord jogger sets; sizing is consistent and they nail the premium casual aesthetic at a great price
Urban Outfitters — one of the best high street brands for streetwear-adjacent women's pieces; oversized tees and heavyweight hoodies are their sweet spot
All Saints — for the darker, more minimal streetwear-meets-fashion girl; their sweatshirts and joggers have real quality and size predictably
Topshop — classic oversized fits done well, particularly in sweatshirts and relaxed co-ords; consistently reliable sizing
H&M — consistently good for basics that work within a streetwear wardrobe; their Divided line does genuinely great heavyweight tees
Superdry — especially strong for graphic hoodies and oversized outerwear; sizing is more generous than average and the quality is genuinely solid
Gymshark — if you want the street-meets-sport look; their Everywear range is particularly good for pieces that blur the line between gym and casual wear

Two Independent Picks

Hoodrich — a Birmingham-born UK streetwear brand with serious credibility. Their women's sizing is more consistent than Certified and the quality is excellent. A great one to know if Certified Sports is your vibe
Oner Active — founded by UK-based trainer Krissy Cela and genuinely brilliant for women who want strength-training gear that looks cool outside the gym. Sizing is true to size and very well thought-out for real bodies

Premium Options

Represent Clothing — if you want to invest in that premium streetwear aesthetic with better size consistency
Vuori — Californian brand now with a London flagship; elevated athleisure with excellent size guides

Luxury / Designer

Sporty & Rich — the cult New York-born label beloved by fashion editors; the sizing is US-based, so do check conversions
Moncler Grenoble — for the ultimate premium logo sweatshirt moment

Never Guess Your Size Again — Use Tellar.co.uk

Certified Sports sizing is genuinely one of the trickier ones to get right — especially if you're ordering online without being able to try it on first. That's exactly why Tellar.co.uk exists.

Tellar is the UK's leading free sizing tool — covering 1,500+ brands including Certified Sports, matched to your exact measurements. No downloads, no subscription, completely free to use.

🔍 Measure once — bust, waist, or hip — and let Tellar do the work
📏 Use the Store Size Lookup Tool to get your precise size in any brand instantly
💡 Works in-browser, no app needed
✅ Always free. Always honest. Always independent.

Plus — the Tellar Fashion Hub has thousands of honest, unsponsored posts from our expert stylists covering every brand, every sizing question, and every style dilemma. No ads, no brand deals, just real advice.

👉 tellar.co.uk