How to Find Your Size in Shirts — And Why It's More Complicated Than You Think

By Ella Blake, Tellar Stylist

Finding your size in shirts comes down to three key measurements: your chest, your neck (for formal shirts), and your sleeve length — but the real trick is knowing which measurement matters most depending on the style of shirt you're buying. Get that right, and a shirt can be genuinely transformative. Get it wrong, and you end up with a great-looking blouse that pulls across the bust or swamps your shoulders entirely.

I've made both mistakes more times than I care to admit. There's a Massimo Dutti shirt still hanging in my wardrobe from 2021 — beautiful fabric, wrong size, completely unwearable — that haunts me every time I open the door. So let me save you from a similar fate.

The Measurements That Actually Matter

Before you buy anything, grab a soft tape measure. You need:

• Chest/bust: Measure around the fullest part of your chest, keeping the tape parallel to the floor. This is your most important measurement for women's shirts and blouses.

• Waist: Measure around your natural waist — the narrowest point, usually an inch or two above your belly button.

• Hips: Measure around the fullest part of your hips, usually about 8 inches below your natural waist.

• Neck (for formal/classic shirts): Measure around the base of your neck and add half an inch for comfort.

• Sleeve length: Measure from the centre back of your neck, over the shoulder and down to your wrist. Crucial for long-sleeved shirts.

Write these down. Seriously — keep them in your phone. You'll thank yourself later.

Fitted vs. Relaxed: They Size Completely Differently

This is where most people go wrong. A tailored, fitted shirt and an oversized or relaxed-cut shirt are sized entirely differently, even within the same brand.

For a fitted shirt — think classic workwear or a tucked-in button-down — your chest measurement is everything. The shirt should skim your body without pulling at the buttons or gaping across the bust. If you're between sizes, always size up. A shirt that pulls across the chest looks far worse than one that's slightly roomy.

For a relaxed or oversized shirt, chest measurement still matters, but you're also dressing for intended fit. A shirt intentionally cut oversized from a brand like COS or ASOS will be labelled to its actual body measurements — if you want the slouchy, borrowed-from-the-boys look, don't size up further than one size.

The Shoulder Seam Test — and Why It's Non-Negotiable

Whether fitted or relaxed, the shoulder seam should sit right at the edge of your shoulder — not sliding down your arm, and not pulling up towards your neck. This is the single best indicator of whether a shirt actually fits you. You can nip in a waist, you can hem a sleeve, but a shoulder seam that's two inches off? That's structural, and it cannot be fixed without significant tailoring.

White Stuff and Boden are both great for shirts with well-positioned shoulders at the mid-range price point. I've found Whistles consistently excellent for fitted shirts that actually sit right across the shoulders without that dreaded diagonal pull across the back.

Button-Front Shirts: Bust Fit is Everything

If buttons are pulling — even slightly — across your bust, the shirt is too small. Full stop. This isn't a styling quirk, it's a fit problem, and it draws attention in all the wrong ways. If you're larger busted, always size to your chest measurement and have the shirt taken in at the waist if needed. M&S is genuinely one of the better high street options here, particularly their Collection range, which gives a more generous cut through the bust without being boxy. Phase Eight and Hobbs also cut well for curves.

For petite frames, Next has a solid petite shirt range that accounts for shorter torsos properly — so you're not drowning in fabric between the buttons and the hem. Jigsaw tends to run slightly longer in the body, which is worth knowing if you prefer to tuck.

Brand Sizing is All Over the Place — Here's What to Know

This is genuinely one of the most frustrating things about buying shirts. Vanity sizing means a size 12 in one brand can fit identically to a size 14 in another, and inconsistencies are rife even within the same brand's different ranges. I've been a different size in three different Reiss shirts bought in the same season. It's maddening.

A few patterns I've noticed:

• Zara runs small — size up at least one, sometimes two sizes, especially in structured shirts.

• Mango is fairly true to size but cut for a narrower frame; if you're broader across the back, check measurements carefully.

• Me&Em runs generously and honestly — their size guides are reliable and their fabrics have enough give to forgive minor fit issues.

• Tommy Hilfiger shirts tend to be cut for a straighter silhouette; if you have curves, size up and belt it.

• Crew Clothing is brilliantly consistent — one of the few brands where I trust the label almost implicitly.

For independent options, Beaumont Organic (a brilliant sustainable label based in the UK) does exceptional relaxed linen and cotton shirts with genuinely helpful size notes on each product page. And Cucumber Clothing — a small British brand specialising in soft, breathable fabrics — sizes beautifully and is worth bookmarking if you haven't discovered them yet.

Don't Forget Fabric — It Changes Everything

A stiff cotton poplin shirt will feel completely different to a silk-blend blouse in the same size. Woven fabrics have no give at all, which means you need to be more precise with measurements. Soft, draped fabrics are far more forgiving. If you're buying a formal, structured shirt in a non-stretch fabric, size to your chest measurement precisely. If it's a soft, drapey blouse, you'll generally have more leeway.

Stop Guessing — Use Tellar to Find Your Size Instantly

Shirt sizing honestly doesn't need to be this stressful. Tellar is the UK's leading free sizing tool — covering over 1,500 brands — and it takes all the guesswork out of the equation completely. You measure once (bust, waist, hips), and Tellar matches your body to the exact size you need at any brand. No more buying two sizes and returning one. No more disappointing deliveries.

• Use the Store Size Lookup to find your precise size at brands like COS, Reiss, M&S, Whistles and hundreds more

• Read the Ultimate Clothing Sizing Guide for a deep dive into how sizing actually works across the industry

• Browse the Ultimate Guide to Jackets if you're thinking about layering those shirts up this season

It's always free, always honest, and always unsponsored. The Fashion Hub is packed with independent style advice from real stylists — no ads, no brand deals, no agenda. Just genuinely useful fashion content.

The bottom line? Measure properly, understand the cut you're shopping for, and stop trusting the label blindly. Shirts are one of the most versatile pieces in any wardrobe — when they fit, they're genuinely unbeatable. It's worth taking the extra two minutes to get it right.