How to Use a Size Chart and Always Buy the Right Size

A size chart only works if you match your own body measurements to it — not your usual size. That is the whole trick, and it is the step almost everyone skips. If you know your bust, waist and hip measurements in centimetres and you read the chart properly, you will buy the right size far more often than you currently do. If you scroll straight past the chart and click "12 because I'm always a 12", you are gambling.

I have been styling for years and I still measure myself twice a year. Bodies change. Brands change. The tape doesn't lie.

Why your "usual size" keeps letting you down

There is no legally enforced sizing standard in the UK. Every brand sets its own block — the base pattern all its garments are cut from — and that block is built around a fit model with a specific body. So a size 12 at one retailer can be four centimetres different across the bust to a size 12 somewhere else.

Then there's vanity sizing, where labels quietly enlarge garments and keep the number the same. It flatters, briefly, and it wrecks your ability to shop across brands.

My own worst example: I once ordered a linen blazer in my "always" size for a client fitting, didn't check anything, and it arrived so tight across the back I couldn't lift my arms past shoulder height. I'd been sizing off habit for about three years. Ten seconds with a tape measure would have caught it.

Step one: measure yourself properly

You need a soft tape measure and, ideally, thin underwear or nothing at all. Measuring over a jumper is the single most common mistake I see — it can add three or four centimetres and completely skew your result.

Bust: around the fullest part, tape level all the way round and flat across the back. Don't pull it tight.
Underbust: directly beneath the bust. Most people ignore this, but it's what determines whether a fitted dress or a wrap top will actually close.
Waist: the narrowest point of your torso, usually just above the belly button. Bend sideways — the crease is your natural waist.
Hips: the fullest part, generally 18–20cm below the waist. Feet together.
Inside leg: from the crotch to the floor, barefoot. Essential for trousers and jeans.
Shoulder to shoulder: across the back, from one shoulder bone to the other. This is the measurement that decides whether a blazer or coat works, and almost nobody takes it.

Write them down in centimetres. Most European and premium charts use cm, and converting on the fly is where errors creep in.

Step two: work out what kind of chart you're reading

This is the part that trips people up more than anything else, and it's genuinely important.

Body measurement charts

These tell you the measurements of the person the garment is designed for. You match your body to the numbers directly. Most high street size guides work this way.

Garment measurement charts

These tell you the dimensions of the actual item laid flat. You need to add ease — the extra room designed into the garment — before comparing. A tailored shirt might have 5cm of ease across the bust; an oversized jumper might have 20cm. If you match your body measurement exactly to a garment measurement, it'll fit like cling film.

If the chart doesn't say which it is, look for a "how to measure" diagram. Body charts show a figure with a tape around it. Garment charts show a flat sketch with arrows across it.

Step three: what to do when you're between sizes

Nearly everyone is. Very few of us match a single column across bust, waist and hips.

Size to your largest measurement, then take it in. A seamstress can nip a waist for very little. Nobody can add fabric that isn't there.
For dresses and tops, prioritise the bust and shoulders. These are structural and expensive to alter.
For trousers and skirts, prioritise the hips, then have the waistband adjusted.
For coats and blazers, prioritise the shoulders. A shoulder seam that sits wrong can't be fixed properly at any price.

Step four: read the fabric before you commit

The composition line does half the work of the size chart.

2–5% elastane gives useful give — you can usually take your true size or size down.
100% cotton, linen or viscose has no recovery. Take your true size, and expect linen to soften rather than stretch.
Bias-cut silk skims and drapes; sizing up is far safer than sizing down.
Rigid denim will relax roughly one centimetre at the waist after a few wears. Stretch denim will not.
Wool knitwear grows with wear and shrinks in the wash. Buy for the shoulders, not the body.

One more thing I've learned the hard way — always check the model information. Most product pages list her height and the size she's wearing. If she's 5'10" in a size 8 and you're 5'3", that midi skirt is going to be a maxi on you. I ordered a slip dress that looked immaculate online, and on me it pooled on the floor like a puddle. Lovely fabric. Completely wrong proportion.

Where the size charts are actually reliable

Some brands publish genuinely useful, accurate data. Others publish a chart and then cut nothing like it. Here's where I send clients.

High street

M&S — the most consistent block on the British high street, with clear body measurement charts and a genuinely broad fit range. My default recommendation for anyone rebuilding their wardrobe basics.
Uniqlo — publishes garment measurements alongside body charts, which is rare and enormously helpful. Their fit is Japanese-standard, so it runs slightly narrow through the shoulder.
Boden — detailed guides, dependable sizing year on year, and a fit block designed around British proportions rather than borrowed from elsewhere.
COS — architectural, generously cut and true to their chart, but the ease is significant. Read the model height and size down if you want anything close to fitted.
Massimo Dutti — grown-up tailoring with accurate European sizing. Consistent shoulder fit across seasons, which matters more than people realise.
Whistles — a narrower, more contemporary block. Excellent charts, but the cut assumes a slimmer frame through the ribcage.
Mango — sharp and inexpensive, but sizing swings between collections. Always check the composition and the model height before buying.
Seasalt Cornwall — relaxed, generous and honest about it. Their guides are clear and their fit is genuinely forgiving.

Premium

Me&Em — obsessive about fit, with detailed guides and multiple lengths on trousers. Worth the money precisely because you get the sizing right first time.
Sézane — French sizing that runs small, but the charts are accurate if you actually read them rather than assuming your UK size translates.
Hush — relaxed British casualwear with reliable, consistent sizing and helpful customer fit notes on most products.
Baukjen — designed for real proportions with clear measurement guidance, and excellent for anyone between a 12 and an 18.

Luxury and designer

Max Mara — Italian sizing, immaculate tailoring and charts you can trust absolutely. Their coats are cut for the shoulder first, which is why they last decades.
Totême — minimal, precise and honest about ease. The charts are accurate but the cut is deliberately loose, so know what you're buying.
Joseph — narrow through the body with beautifully engineered trousers. Size up if you're between, and get the length altered.

Two independents worth knowing

Aligne — a London label publishing garment measurements on every single product page. Considered, wearable design and one of the most transparent sizing pages I've come across.
Albaray — founded by a team of former high street buyers who clearly cared about fit. Grown-up, well-cut pieces with sizing that behaves exactly as the chart promises.

Your quick pre-purchase checklist

Measure yourself in centimetres, over nothing or thin underwear
Identify whether the chart is body or garment measurements
Size to your largest measurement and alter down
Check the fabric composition for stretch
Check the model's height and the size she's wearing
Read the recent reviews for fit comments — they're the most honest data on the page

Never Look at a Size Guide Again

All of the above is exactly why I built Tellar — the UK's leading sizing tool. You measure once, and your body is matched instantly to over 1,500 brands. No more decoding charts on every product page.

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

There's also the Tellar Fashion Hub: a library stacked with free posts from our top stylists. Honest, unbiased, independent and always free. Style advice, top picks and the best brands.

Find your size at tellar.co.uk →