How Do I Find My Size in Tops? The Honest Guide to Getting It Right Every Time

By Ella Blake, Tellar Stylist

Finding your size in tops is genuinely one of the trickiest parts of shopping — and I say that as someone who has been dressing women professionally for years. Your size in a top depends on far more than the number on a label, and the sooner we all accept that, the better our wardrobes will look. The short answer: measure your bust, know your shoulder width, and always check the brand's size guide — because a size 12 in M&S is absolutely not the same as a size 12 in Zara.

Let me save you the heartbreak I've witnessed (and personally experienced). I once ordered a beautifully structured blazer from Reiss in my usual size, smug as anything. It arrived, I put it on, and the shoulders sat about an inch past mine. It looked like something I'd borrowed from a taller friend. I had missed one crucial measurement — the shoulder seam. Since then, I never shop for tops without checking three things: bust, shoulder, and length. Here's how to do it properly.

Start with the Right Measurements

Before anything else, grab a soft tape measure. You're going to need three key measurements for tops:

Bust: Measure around the fullest part of your chest, keeping the tape parallel to the floor. Don't pull it tight — you want it snug but comfortable. This is your most important measurement for fitted tops and shirts.
Shoulders: Measure from the edge of one shoulder seam to the other, across your upper back. This is critical for structured tops, blazers, and shirts — if the shoulders don't fit, nothing else will.
Length: From the top of your shoulder down to wherever you want the hem to fall. So useful for knowing whether a top will be cropped on you or not.

Write these down. Seriously, keep them in your phone notes. You will use them constantly.

Why Your Usual Size Doesn't Always Work

Here's the thing nobody tells you in enough detail: clothing brands cut tops differently depending on their target customer. Cos cuts with a relaxed, Scandinavian ease — their tops are often roomier in the body. Whistles cuts more precisely through the shoulder and upper chest. Phase Eight tends to be generous through the bust. Mango runs on the smaller side across the shoulders, in my experience, which I learned the hard way with a silk blouse that pulled uncomfortably all day.

This isn't about your size being wrong — it's about brands being inconsistent. It's maddening, and it's why so many women end up with tops that gape at the chest or pull across the back. The key is treating each brand separately and consulting their size guide every single time, rather than assuming.

Fitted Tops vs. Relaxed Tops: Different Rules Apply

The fit you're aiming for completely changes which measurement you should prioritise:

Fitted or tailored tops (shirts, blazers, structured knits): Prioritise bust and shoulder measurements. If you're between sizes, go up — you can always add a belt or tuck it in.
Relaxed, oversized or draped styles: Focus on shoulder width as your anchor point. The body of the top is meant to be loose, but if the shoulders are too wide, it will look shapeless rather than intentionally relaxed.
Stretch tops (jersey, ribbed, bamboo): These are more forgiving — go by bust measurement, and if you prefer a close fit, size down one. Brands like Me&Em and Mint Velvet do excellent stretch-jersey tops that have great recovery and hold their shape well.

What to Do If You're Between Sizes

So your bust puts you in a 14 but your shoulders are a 12 — what then? This is genuinely common and not a problem you need to solve by finding a "perfect" brand. Here's how I approach it:

For structured tops and shirts: size to your shoulders. A top that fits well across the back but is slightly loose in the body can be taken in by a tailor for very little money — but a tight shoulder cannot be fixed.
For knits and jersey tops: size to your bust. The give in the fabric means the shoulders will follow.
For wrap tops: size to your bust, as these are adjustable at the waist anyway — brilliant if you're between sizes.
If you're larger-busted, look at brands with a wider range of cup sizing in their tops. Boden offers some styles in bust sizes, and independent brand Pepperberry — part of the Bravissimo family — is exceptional for curvy-busted women, with tops designed to fit D cup and above without the pulling-across-the-chest issue that drives so many women to despair.

High Street Brand Tips: What Fits Whom

I've spent enough time in changing rooms across every high street brand to have some firm opinions on fit:

Hobbs — beautifully cut shirts and blouses, tends to run true to size through the shoulder. A solid investment-piece brand.
Anthropologie — lovely but often runs small. Size up at least one, especially in their fitted tops.
Jigsaw — cuts with a slightly longer length, which is brilliant if you're tall or want tops that stay tucked. Quality fabric too.
White Stuff — generous sizing, great for fuller busts. Their linen tops in particular are excellent for summer.
Oliver Bonas — more fashion-forward, and tends to run on the smaller side. Check reviews before buying online.
Great Plains — consistently well-fitting basics, slightly relaxed cut. One of the underrated staples of any grown-up wardrobe.
Hush — beautifully relaxed sizing, but check the length — their tops can come up quite long depending on the style.

For something a bit more under-the-radar, I'd also recommend Nrby — a small independent knitwear brand with an exceptional fit and the most useful size notes I've seen from any label. Worth bookmarking if you haven't already.

The One Thing Most People Skip

Read the product description. I know, I know — it sounds obvious. But most people skip straight to size and add to basket. The description will often tell you whether a top runs small, is designed with a relaxed fit, or has a cropped hem. That information is gold. Combine that with your measurements, and you'll dramatically reduce the number of returns you're making.

Never Guess Your Size Again — Use Tellar

This is exactly why I love Tellar.co.uk — it does all of this size-matching work for you, across 1,500+ brands, instantly. You enter your measurements once and Tellar tells you your precise size in whatever brand you're shopping. No more guessing, no more returns, no more frustrated evenings surrounded by packaging.

It's particularly brilliant for tops, where brand-to-brand variation is so significant. Use the Tellar Store Size Lookup to find your exact size at brands like COS, Reiss, Arket, Everlane and hundreds more. It's free, works in your browser, and there's nothing to download.

Want to go deeper on sizing? The Ultimate Clothing Sizing Guide is the most comprehensive free resource I've seen on the subject — covering everything from how vanity sizing works to why your measurements matter more than the label. And if you're working out what to wear with your tops, the Ultimate Guide to Jackets is a brilliant companion read.

Tellar's Fashion Hub is a completely free, independent library of style advice — no ads, no sponsored content, no brand bias. Just honest, expert guidance you can actually trust.