What Is Sizing Like at Agnès b?

Agnès b. runs small, and you will very often need to size up by one — sometimes two. This is a proper French house that has stuck to authentic Continental sizing since 1973, so it has never absorbed the gentle size inflation we have all quietly enjoyed on the British high street. If your usual size felt suspiciously generous in COS last week, Agnès b. is about to be the cold splash of water that corrects it.

The other thing that catches people out is the labelling. Agnès b. doesn't use UK 8, 10, 12. It uses its own "T" system — T0, T1, T2, T3 and so on — and there is no friendly translation printed on the swing tag. So before we get to the fit, let's decode what those numbers actually mean.

The Agnès b. "T" sizing system, in plain English

The "T" stands for taille — simply "size" in French. The numbers climb in single steps rather than the 8-10-12 jumps you're used to, and because the cut is genuinely close, my rule of thumb is to read them on the snug side:

T0 — roughly a UK 6–8, but cut lean. A true 8 will usually want T1.
T1 — sits around a UK 8–10. If you're a fitted 10 you'll likely be happiest going up.
T2 — broadly a UK 12–14, and the size I'd point most 12s towards.
T3 — generally a UK 16–18.
T4 and up — continues the pattern, though the upper range is limited, which is worth knowing if you're above a UK 18.

Treat that as a starting point, not gospel. Agnès b. publishes garment measurements on every product page, and with this brand they genuinely matter — check the bust and the length before you commit, because the cut does most of the talking.

How it actually fits, garment by garment

The snap cardigan and knitwear

The pressed-stud snap cardigan is the piece everyone comes for, and it is cut close — narrow through the shoulder, neat in the sleeve, designed to sit like a second skin under a blazer. If you want it to layer over a shirt, or you prefer any ease at all across the bust, size up. I learned this the hard way: my first snap cardigan, bought in my "normal" size on a giddy afternoon in Paris, fit like a sausage skin and the studs gaped the moment I sat down. The replacement, one size up, has been in steady rotation for six years. Lesson banked.

Breton tops and jersey basics

The famous striped tees and fine cotton jersey are where the small-sizing is most obvious. The body is slim and the sleeves are slim, so unless you specifically want that neat 1960s Left Bank silhouette, take the larger option. The cotton is beautiful but firm — it doesn't have much give, and it won't relax dramatically in the wash.

Tailoring and trousers

The jackets and trousers are where Agnès b. earns its money — sharp, architectural, very Parisian. They're also the least forgiving, so I always advise sizing for your largest measurement (usually the hip or bust) and having the rest taken in by a tailor. A good alteration on a £200+ jacket is money well spent and the difference between "smart" and "spectacular."

Dresses

Dresses follow the house rule: lean through the waist, modest in the bust. Anything described as fitted or bias-cut should be tried a size up if you're between sizes. The swing and trapeze shapes are more relaxed and the safest bet if you're ordering blind.

My honest take

Agnès b. isn't difficult once you accept that it's French and proud of it. The pieces are beautifully made, they age for decades, and the restraint is the whole point — this is quiet, grown-up dressing, not fast fashion. The win is buying something that still looks current ten years on. The trap is buying your "usual" size out of habit and ending up with a wardrobe of gorgeous things you can't lift your arms in. When in doubt, go up.

Where else to shop for that pared-back French look

If Agnès b.'s fit, price or availability doesn't land for you, here's where I'd send clients for the same effortless, Left-Bank ease — split by budget.

High street

COS — the closest high-street cousin to Agnès b.: architectural, minimal, brilliant fine knits. Sizing is more generous, so you're on safer ground.
Whistles — clean, contemporary tailoring with a quietly French sensibility and a slightly roomier cut.
Uniqlo — unbeatable for the jersey basics and fine merino that sit under everything; the Breton-style tees are a fraction of the price.
Jigsaw — understated British quality with the same grown-up restraint; lovely trousers and knitwear.
Massimo Dutti — elevated European tailoring that punches well above its price for that polished Continental finish.
Boden — the high street's most reliable home for a proper Breton stripe done with charm.
Hush — relaxed French-girl staples — the easy linen, the slouchy knit — with a forgiving, modern fit.

Premium

Sézane — the obvious step-across: the same Parisian chic as Agnès b. but with friendlier, closer-to-UK sizing and a cult following for good reason.
Ba&sh — French contemporary with a softer, prettier hand than Agnès b. and a little more ease through the body.
Totême — Scandinavian minimalism for the woman who loves Agnès b.'s lines but wants a more relaxed, modern drape.

Luxury / designer

A.P.C. — fellow French minimalist royalty; slightly more generous than Agnès b. while keeping that pared-back Parisian look intact.
Lemaire — architectural, oversized and entirely sizing-stress-free, for when you want the French intellectual wardrobe at its most directional.

Two independents worth knowing

Bellerose — a Belgian label with proper French-girl DNA: relaxed Bretons, easy shirting and unfussy tailoring that layers beautifully and runs true to a comfortable, lived-in fit.
Sœur — a Parisian independent beloved by the fashion crowd for grown-up, slightly schoolgirlish pieces with a clean cut and gorgeous fabrics; a genuine hidden gem.

How Tellar takes the guesswork out of it

Decoding a "T2" against your UK size is exactly the sort of faff I got tired of, which is precisely why I built Tellar.

Tellar is the UK's leading sizing tool: your body, matched exactly to 1,500+ brands, instantly. Never squint at a size guide again. And alongside it sits the Tellar Fashion Hub — a library stacked with free posts from our top stylists. Honest, unbiased, independent and always free.

Measure once — using your bust, waist, hip, or simply a brand size you already wear.
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Ella Blake — Senior Fashion Stylist & Founder, Tellar