What Is Sizing Like at Sébline?

Sébline runs relaxed and a touch oversized. It is a shirting house at heart, so the cut leans roomy with a generous shoulder and an easy body rather than anything nipped in. Most women can take their usual size for that effortless, slightly borrowed-from-the-boys look, or drop down a size if they want something sharper and closer to the body. If you only read one line before you check out, that is it: think of Sébline as the perfect oversized poplin shirt, and size with that in mind.

I have styled enough shirting labels over the years to know that the letter on the label tells you almost nothing here. The fit philosophy matters far more than the size code, and Sébline has a very particular one. Let me walk you through it properly.

Who is Sébline, and why does the fit feel different?

Sébline is the namesake label of Charles Sébline, a Franco-British designer who trained inside some of the most exacting ateliers in fashion. Before launching his own line in 2019, he worked under Yves Saint Laurent and passed through Vivienne Westwood and Azzedine Alaïa. That pedigree shows in every seam.

It is a tightly edited range, mostly cotton poplin shirts, with the occasional pyjama-style set and tailored piece.
The cut references Savile Row tailoring and old-school uniform shirting, so it is structured at the shoulder but deliberately easy through the body.
Those signature stripes are cut on-grain and matched at the seams. That precision is the whole point of the brand.
The poplin is woven to soften with every wash, so a shirt that feels crisp on day one drapes more fluidly within a month.

Because these are genuinely designed as throw-on-and-go pieces, the silhouette is roomier than a typical fitted women's blouse. That is intentional, not an error in the cut.

How Sébline actually fits — my stylist notes

Boutique, French-leaning sizing. Do not assume a high-street medium maps neatly across. Check the brand's own measurements against a shirt you already love.
Shoulders sit slightly dropped. This is part of the relaxed line, not a fault. It is what gives the shirts their easy, lived-in shape.
The body is generous. If you are between sizes and want something sharp and tucked, size down. If you want that undone, oversized look, stay true to size.
Sleeves run long — very French. Roll the cuffs; they are designed to be worn that way and the turn-back is half the charm.
Bust-led fit is forgiving. The roomy cut means a fuller chest is rarely the problem it can be with slimmer European shirts.

Here is a real example. I dressed a client last winter who bought her usual size and adored how it looked thrown open over a silk slip — all that lovely volume. Another client, who wanted hers crisp and tucked into wide trousers, sized down and got a far more tailored result. Both were right. With Sébline, the size you take genuinely depends on the outfit you have in mind.

And a confession, because I have made the mistake myself: years ago I bought a luxury poplin shirt online in my "safe" size without checking the cut, and it swamped me completely — sleeves past my knuckles, shoulders halfway to my elbows. Lesson learned. With shirting labels especially, read the fit notes before you read the size label.

How I'd style a Sébline shirt

Tuck into tailored trousers, collar up, sleeves rolled — the full Left Bank look.
Worn open over a vest or slip dress as a light layer for spring evenings.
Half-tucked into straight-leg jeans with loafers for an off-duty weekend.
A striped style under a navy blazer instantly reads more polished than a plain white shirt.

Where else to shop a brilliant shirt, by budget

Sébline is a real investment, so if you love the look but want options at every price point, these are the shirt specialists I send clients to. I have chosen each one specifically for its shirting, not just its name.

High street

Uniqlo — their Supima cotton poplin shirts are sharp, crisp and ridiculously good value.
M&S — dependable pure-cotton shirts with reliable, consistent sizing.
COS — clean, architectural shirting with the relaxed, slightly oversized cut Sébline fans will recognise.
Gant — a genuine shirt heritage brand; their oxford and poplin styles are preppy and beautifully made.
Boden — the place for a proper Breton-striped shirt with a bit of personality.
Massimo Dutti — elevated poplin and quietly excellent Spanish tailoring for the money.
Whistles — refined, contemporary shirts that feel a notch above the rest of the high street.
Hush — easy, everyday shirting in lovely soft cottons for relaxed days.

Premium

Joseph — beautifully cut poplin and elevated minimalism; the closest premium feel to a designer shirt.
Toast — artisanal fabrics and a softly relaxed line, perfect if you love the lived-in Sébline texture.
Sézane — the French-girl shirt done brilliantly; the Tomboy style is a cult buy for good reason.

Luxury & designer

Totême — immaculate Scandi-luxury poplin with that effortless, expensive-looking restraint.
Max Mara — structured, investment shirting designed to last decades, sitting in the same world as Sébline.

Two left-field independents worth knowing

With Nothing Underneath — a British cult label that does the perfect oversized white shirt and very little else, much like Sébline's single-minded focus.
Deiji Studios — an Australian slow-fashion brand making gorgeously relaxed organic-cotton shirting; genuinely under the radar in the UK.

Never guess your size again — meet Tellar

Tellar.co.uk is the UK's leading sizing tool. It matches your body exactly to more than 1,500 brands instantly, so you never have to squint at a size guide again. Here is how it works:

Measure once, using your bust, waist and hip — or simply your existing size in a brand you already know.
Use the Store Size Lookup tool to get your precise size in any brand — COS, Reiss, Everlane, Arket and more.
Always free, no downloads needed — it works straight in your browser.

And there is the Tellar Fashion Hub too: a library stacked with free posts from our top stylists. Honest, unbiased, independent and always free — style advice, top picks and the best brands, all in one place.

More from the Tellar Fashion Hub

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Ella Blake — Senior Fashion Stylist & Founder, Tellar