Why Do Designer Brand Clothes Run So Small?

Yes — designer clothes genuinely do run smaller than the high street, and it's not your imagination (or your waistline). I've spent years styling clients and shopping everything from Zara to Chanel, and the sizing discrepancy is very real. There's actually a fascinating mix of history, psychology, and pure commercial strategy behind it. Once you understand why, you'll never feel deflated in a designer changing room again — and more importantly, you'll know exactly how to shop smarter.

It Started With European Sizing

A lot of the confusion comes down to where luxury fashion was born. The great French and Italian houses — think Celine, Jacquemus, Loro Piana — developed their sizing systems decades ago based on a very specific sample size, one that bears little relation to the average woman's body in 2025. European sizing runs notoriously narrow in the bust and hip, and the conversion charts are all over the place. A French size 38 is roughly a UK 10, but in a couture-cut blazer it might squeeze a UK 8.

I remember taking a client to try on a beautiful Saint Laurent blazer — she's a confident size 10 across every high street brand she owns. We had to ask for a size 44. She looked incredible in it, by the way. The number on the label is completely irrelevant; the fit is everything.

The "Aspirational Fit" Theory — And Why Brands Use It

Here's the uncomfortable truth: some luxury brands have historically used smaller sizing quite deliberately. The idea is aspirational — if a garment feels snug, you're meant to aspire to fit into it rather than question the cut. It's the opposite of the "vanity sizing" you see on the high street (where brands run slightly large to make you feel good). Designer brands have traditionally leaned the other way.

This is slowly changing. More progressive luxury labels like Toteme and The Row offer generous, oversized silhouettes that feel inclusive without compromising on elegance. But the old guard? Still quite unforgiving.

The Way Designer Clothes Are Cut

There's also a structural reason for the tighter feel. Designer garments are often constructed with far less ease allowance — that's the extra fabric built in above your body measurements to allow you to actually move. High street brands build in considerable ease to make clothes comfortable for a wide range of bodies. Luxury tailoring is cut closer to the body, almost like a second skin, which is beautiful in principle but means sizing up is often unavoidable.

• Jackets and blazers: Almost always size up at least one, sometimes two sizes

• Trousers: The waist is usually the sticking point — try sizing by your hip measurement instead

• Knitwear: Can vary wildly — cashmere from some Italian labels comes up very small in the body

• Dresses: Waist and bust proportions can be dramatically different to UK sizing norms

How to Shop Designer Without the Fitting Room Heartache

The single best thing you can do is know your measurements — not your dress size, your actual centimetres. Bust, waist, hips. Once you have those, you can cross-reference against a brand's own size guide. Most luxury brands publish detailed measurement charts on their websites; use them religiously.

On the high street, you'll find sizing far more forgiving and consistent — though still not perfect, which is a whole other conversation. My go-to brands when I want something that fits brilliantly without the guesswork:

• Cos — cuts consistently across its range, true to a relaxed European fit, brilliant for minimalist tailoring

• Mango — reliable sizing, especially in dresses and tailored separates; tends to have a slightly more fitted Mediterranean cut

• Massimo Dutti — one of the most consistent on the high street for tailoring; I always recommend sizing as you would in Zara

• Jigsaw — excellent for women with fuller busts; they cut generously through the chest while keeping a clean line

• Reiss — generally true to UK sizing, though their structured pieces can run narrow across the back

• Me&Em — sizing is reliable and the proportions tend to flatter a range of body shapes without drama

• Whistles — consistently sized and beautifully cut; a brilliant middle ground between high street and premium

Premium Brands Worth Knowing

If you're stepping up from the high street but not quite ready for full designer prices, there are some brilliant premium options that get sizing right. Toteme is perhaps the best at this — every piece I've styled from them has fitted beautifully across UK 8–18. Sandro runs slightly small (French brand, see above) but is transparent with measurements. Isabel Marant Étoile — the diffusion line — runs truer to size than the main collection.

Two independent labels I'm particularly obsessed with at the moment: Kitri, a London-based brand with genuinely brilliant proportions and inclusive sizing that goes up to a size 26, and Lisou, a small British label known for its silk pieces — they cut beautifully and the sizing is clear and consistent. Both are well worth a look if you haven't come across them.

The Luxury Reality Check

At the luxury end, go in with zero ego and full measurements. Jacquemus runs very small — I'd suggest sizing up two in almost everything. Celine (under Hedi Slimane's direction) became notably more fitted — an effect that's lingered. Max Mara is the notable exception: their coats run generously and are one of the most reliably well-sized luxury purchases you'll make. Their camel coats come up large in the shoulder, which I personally love — it gives that effortless, slightly borrowed-from-the-boys feel.

The bottom line: sizing up in designer is not a defeat — it's just how it works. The label inside the collar means nothing. The fit on your body means everything.

Never Guess Your Size Again — Tellar Has You Covered

This is exactly why Tellar.co.uk exists — and honestly, it's the tool I wish I'd had when I started styling. Tellar is the UK's leading sizing tool, matching your body measurements to over 1,500 brands instantly. No more guessing, no more size charts, no more sending things back.

Here's how it works:

• Measure once — bust, waist, and hips (or just use your size in a brand you already know fits you well)

• Use the Store Size Lookup tool to get your precise size in any brand — from Cos and Reiss to designer labels and everything in between

• Works in-browser, no downloads, always free

It's genuinely brilliant for exactly the kind of designer sizing issues we've been talking about. Trying to work out if you're a 38 or a 40 in a French brand? Tellar tells you in seconds.

Explore the Tellar Fashion Hub

Beyond the sizing tool, Tellar has a full Fashion Hub — a free library of style guides and best-buy edits written by stylists. Honest, unbiased, and never sponsored. A few posts worth bookmarking:

• The Ultimate Clothing Sizing Guide — everything you need to know about how sizing works across brands

• Jeans Trends 2026 — the cuts worth investing in right now

• Ultimate Guide to Dresses & Best Buys — styles, body shapes, and where to shop

• Ultimate Guide to Jackets & Best Buys — how to find your best fit across every style

Visit tellar.co.uk — free to use, no sign-up required, and it might just save you a very frustrating afternoon in a Parisian dressing room.