Clothes Sizing Explained: How to Get Your Size Right, First Time

By Ella Blake, Senior Fashion Stylist & Founder

There is no legal or universal standard for clothing sizes, which is why a size 12 in one shop is a comfortable 10 in another and a strangled 14 somewhere else. Every brand builds its clothes on its own fit block and its own fit model, so the number on the label tells you almost nothing about whether a garment will actually fit you. The only reliable route to getting your size right is to know your body measurements and match them to the individual brand — not to trust the label.

I have been styling for years and I still have everything from an 8 to a 16 hanging in my own wardrobe. That is not a wardrobe problem. That is a sizing problem, and it is the industry's, not yours.

Why Sizes Vary So Much Between Brands

Three things are going on behind the scenes:

The fit block. Every brand has a master pattern built around a specific body shape. Some are cut for a straighter frame, some for a fuller hip, some for a shorter torso. The block is the single biggest reason sizes differ.
The fit model. Brands fit samples on a real person. If that person has a 68cm waist and you have a 74cm waist, the proportions will land differently on you regardless of what the label says.
Vanity sizing. Sizes have quietly crept upwards for decades. A 1970s size 12 is roughly today's size 8. Brands with a long heritage and brands chasing a younger customer sit at opposite ends of that scale.

Add ease — the deliberate extra room a designer builds in — and you can see why two garments with identical labels can differ by 10cm across the bust.

How to Measure Yourself Properly

This takes four minutes and it will save you a fortune in return postage. Strip to your underwear, wear the bra you'd normally wear with the garment, and keep the tape snug but not pulling.

Bust: around the fullest part, tape level all the way round and not riding up at the back.
Waist: the narrowest point of your torso, usually just above the navel. Don't hold your breath in — I promise the tape is not judging you.
Hips: around the fullest part of your seat, usually 20–22cm below the waist.
High hip: across the top of the hip bone. This is the measurement that decides whether jeans do up.
Inside leg: from crotch to floor, barefoot. Essential for trousers.

Write them down. Re-measure every six months or so, and always after any real change in weight or training.

Read the Garment, Not the Label

Once you have your numbers, the next skill is reading what's in front of you:

Fabric first. Anything with 2% elastane will forgive a centimetre or two. Rigid cotton, linen and structured wool will not. If a blazer is unlined and rigid, size up.
Check the shoulder seam. On tailoring it should sit at the edge of your shoulder bone. Shoulders are the hardest thing to alter, so buy for the shoulder and take the waist in.
Buy for your largest measurement. If your hips are a 14 and your bust is a 10, buy the 14 and have the rest adjusted. A good tailor charges less than you think.
Between sizes? Size up in tailoring and outerwear, size down in knitwear and jersey. Knit relaxes with wear; a jacket never will.
Read the reviews for fit, not for stars. "Runs small" said forty times is data.

My most expensive lesson: a French label blazer I bought in my usual size without checking. It arrived beautifully made and completely unwearable across the back. French and Scandi brands are frequently cut narrower through the shoulder and arm than British ones — I now size up automatically and I have never regretted it.

Where to Shop, by Fit

High Street

M&S — the most consistent sizing on the high street, and the widest range of fits: petite, tall, curve and long-length in most core lines.
Uniqlo — reliably true to size with genuinely useful short and tall options. Their fabric information is the clearest of any mass retailer.
Next — excellent for anyone caught between standard sizes, with petite, tall and curve running through almost everything.
Boden — cut generously through the hip and bust, and one of the few brands that shows the same garment on several body types.
COS — deliberately relaxed and oversized. Size down at least once unless you want a genuinely voluminous look.
Mango — runs noticeably small, especially in tailoring and outerwear. Assume you are one size up from your usual.
Seasalt Cornwall — roomy, comfortable cuts with a soft fit block. Ideal if you find high-street tailoring restrictive.
Massimo Dutti — beautiful fabric, narrow shoulder line. Buy for the shoulder and adjust elsewhere.

Premium

Me+Em — the best-thought-out proportions in the premium market, with proper long-length and petite ranges rather than a shortened hem.
Hush — relaxed, forgiving sizing and consistent between collections, which is rarer than it should be.
Baukjen — designed around real proportions with a slightly longer body length; strong for anyone with a long torso.
Paige — my go-to for denim when you need stretch recovery. Their high-rise blocks fit a fuller hip properly.

Luxury & Designer

Toteme — minimal, oversized by design. The fit is intentional, so resist the urge to size down too far.
Joseph — precision tailoring with a narrow, elegant block. Try before you commit.
Max Mara — Italian sizing, cut long through the sleeve and body. Superb if you are taller.

Two Independents Worth Knowing

If standard sizing has never worked for you, start here.
Aligne — a London brand with a slightly generous, contemporary block and unusually honest fit notes on every product page.

How Tellar Takes the Guesswork Out

This is exactly why I built Tellar. It is the UK's leading sizing tool: your body, matched precisely to over 1,500 brands, instantly. No more squinting at size guides.

Measure once — bust, waist and hip, or simply enter a brand size you already own and know fits.
Use the Store Size Lookup to get your exact size in any brand — COS, Reiss, Everlane, Arket and 1,500 more.
Always free, no downloads, works straight in your browser.

Alongside it sits the Tellar Fashion Hub — a library of free posts from our stylists on style advice, top picks and the best brands. Honest, unbiased, independent and always free.

Never look at a size guide again

Measure once and Tellar matches you to your correct size in over 1,500 brands — instantly, and completely free.

Find your size now →