What Is Sizing Like at COS?

COS runs large — often significantly so — and that is entirely by design. Their Scandinavian-rooted, architectural aesthetic is built on volume, drape and ease, which means that if you walk in expecting standard UK high-street sizing, you'll walk out confused and possibly swimming in fabric. Size down in tops, shirts and knitwear as a starting point. Trousers and tailored pieces, however, tend to sit closer to true size. Once you understand the logic behind the brand, shopping COS becomes genuinely one of the most satisfying experiences on the high street — but you do need to know the rules first.

I'll be honest — my first COS experience was a mild disaster. I picked up what I thought was a beautiful oversized linen shirt in a size 10 and assumed the oversized label was just a style description. Reader, I looked like I'd borrowed my dad's work shirt. The thing was enormous. Once I learned to size down — sometimes twice in knitwear — everything clicked into place. I now wear COS more than almost any other brand in my wardrobe, and I recommend it to clients constantly. It just needs a proper introduction.

The COS Sizing Philosophy: Why It's Different

COS (Collection of Style) isn't trying to follow your body — it's trying to create a silhouette around it. Think sculptural drape, clean lines, and garments that move with you rather than cling to you. This is deeply intentional, influenced by art, architecture and Scandinavian minimalism. The result is clothing that looks extraordinary when sized correctly, and utterly shapeless when it isn't. The brand uses EU numbered sizing (XS/34, S/36, M/38, L/40, XL/42) as well as the standard S/M/L system, and the clothes also tend to run long — brilliant if you're tall, something to factor in if you're petite.

Garment-by-Garment: What to Expect

Tops, shirts and blouses: Size down by one, sometimes two sizes. Their classic shirts are cut with significant ease through the body and sleeve. A UK 12 will typically find a COS Small or size 36 gives a flattering, still-relaxed fit rather than a tent.
Knitwear and jumpers: Size down — this is where the oversizing is most extreme. The TikTok fashion crowd have a phrase for it: "sizing down twice in knitwear but up in everything else." That's not far off. A COS knit in your usual size can feel shapeless; one size down usually looks intentionally relaxed and beautifully structured.
Dresses: Depends on the style. Their jersey and slip dresses sit closer to true size, while A-line and cocoon shapes are generous — size down if you don't want to be overwhelmed. Structured woven dresses tend to be more true to size.
Trousers: This is where COS behaves more normally. Their tailored trousers and wide-leg styles sit close to standard UK sizing, and in woven fabrics can even run slightly small through the waist. Stick to your usual size here, or check the specific measurements on the product page.
Coats and blazers: This one catches people out the other way — if you want to layer underneath, you're fine in your usual size. But COS's drop-shoulder cuts mean that for some shapes (particularly broader shoulders), the armhole placement can feel awkward. Try before you buy where possible.
Trousers — leg length: They run long. If you're under 5'6", factor in a trip to the tailor or check whether the specific style comes in a shorter inseam. It's worth it.

My Top Tips for Shopping COS

Always check the individual product page for garment measurements — COS does publish these and they're genuinely useful. Don't rely solely on the size guide.
If you're shopping online, start with their jersey pieces and dresses before committing to outerwear. The risk is lower and you'll get a feel for how their sizing works on your specific body.
Don't be embarrassed about going into a store and trying two or three sizes of the same piece. It's genuinely necessary here, and the staff are used to it.
Petite shoppers — be cautious. The combination of generous cut plus long lengths can make COS a frustrating brand. Cropped styles and shorter cuts are your best friends, and sizing down is non-negotiable.
The sales (Black Friday through to January, and late June) are when to invest in outerwear and knits — you can often find 50% off previous season pieces that are just as wearable.

If You Love COS — What Else Should You Shop?

COS occupies a specific spot: better than standard high street in quality and design, without crossing into full designer territory. Here's where to look depending on your budget:

High Street

Whistles – One of the closest alternatives on the UK high street for minimalist, well-cut tailoring. Their sizing is more conventional (closer to standard UK) so slightly easier to navigate, and the quality-to-price ratio is excellent.
Jigsaw – Beautifully made, classically cut and wonderful for elevated basics. Sizing is generally true to size, which makes it a reliable stepping stone if COS's sizing has done your head in.
Mango – For trend-led minimalist pieces at a lower price point. Sizing runs slightly small so size up from COS — but their tailored trousers and blazers are particularly strong right now.
Me&Em – A brilliant British brand for polished, wearable pieces with excellent fabric quality. More fitted than COS but with a similarly grown-up, unfussy aesthetic. Sizing is true to size throughout.
Massimo Dutti – Part of the Inditex family but a world away from Zara. Beautifully tailored, restrained and excellent for workwear. Sizes run close to standard UK, slightly on the smaller side — check measurements on tailored pieces.

Premium

Reiss – A step up in price but not by a huge amount, and the tailoring is genuinely excellent. Runs true to size with a slightly fitted cut — very different to COS's volume-first philosophy but a great brand to mix in for more structured pieces.
Claudie Pierlot – A French brand with a more romantic, feminine edge than COS, but similarly high-quality fabrics and considered design. Sizing runs true to EU sizing so similar logic applies to COS in some styles — size up if between sizes.
Hush – Softer and more relaxed than COS but with a similarly unfussy aesthetic and a strong knitwear and basics offer. True to size throughout and brilliant for everyday wardrobe-building.

Luxury / Designer

Max Mara – If COS is your gateway drug, Max Mara is the destination. Similarly architectural in silhouette, similarly generous in cut, but with extraordinary fabric quality and construction. Sizing is notably generous — typically size down here too. Worth every penny for a coat that will last a decade.

Two Independent Brands Worth Knowing

Nue Notes – A Copenhagen-based independent label that shares COS's Scandi minimalist DNA but with a slightly more playful, contemporary edge. Sizing tends to run true to EU size — think slightly generous cuts in a beautiful colour palette. Hard to find on the UK high street but available online, and genuinely worth seeking out.
Aligne – A British sustainable independent that produces beautifully made, low-impact fashion at an accessible price point. Brilliant structured tailoring with a considered colour palette that will appeal to any COS devotee. Sizing runs true to UK size and the quality is excellent for the price.

Stop Guessing Your COS Size — Use Tellar

COS sizing is genuinely one of the trickiest on the high street — not because they're inconsistent, but because their design philosophy is so different from everything else. That's exactly the problem Tellar solves.

Tellar is the UK's leading free clothing size tool. You measure once — bust, waist, hips — and Tellar instantly matches your exact body to the right size across 1,500+ brands, including COS. Whether it's a linen shirt, a tailored trouser or an oversized knit, Tellar tells you precisely which size to order — no guesswork, no returns, no dressing-room panic.

✔ Measure once — works across 1,500+ brands
✔ Works with COS's EU sizing and S/M/L sizing system
✔ Completely free — no downloads, no subscription
✔ Works in-browser on any device

And when you're done sizing up, head to the Tellar Fashion Hub — a library of thousands of honest, unbiased, unsponsored posts from our stylists. No ads, no sponsored content. Just genuinely good fashion advice, always free.

Visit TellarTry the Store Size Lookup Tool