How Does Sizing Vary by Store for T-Shirts?

T-shirt sizing varies dramatically between stores—a size 12 at Zara can fit like a 10 at M&S or a 14 at COS, because each brand creates their own sizing chart based on their target customer and fit philosophy. I've spent years navigating these inconsistencies as a stylist, and honestly, it's one of the biggest frustrations my clients face. The key is understanding which brands run large, which run small, and how to decode their sizing systems before you buy.

Why T-Shirt Sizing is So Inconsistent

Unlike tailored pieces, T-shirts should be straightforward—but they're not. European brands tend to cut slimmer and shorter, whilst American brands often allow for more room. Then you've got the fabric factor: a cotton jersey tee will fit differently to a modal blend or a thick organic cotton. Add to this the rise of oversized fits, boyfriend cuts, and cropped styles, and suddenly a "medium" could mean anything from skin-tight to slouchy.

I always tell clients to ignore the size label and focus on measurements. A brand's size 12 chest measurement might be 96cm, whilst another's is 101cm—that's a significant difference when you're shopping online. The cut matters too: some brands design for a straight body shape, others for more curves. Boden and White Stuff, for instance, tend to be generously cut with a relaxed fit, perfect if you prefer a comfortable feel. Meanwhile, Mango runs noticeably smaller and suits a more European, streamlined silhouette.

High Street Heroes for Consistent Sizing

Let me share which high street brands I trust for T-shirt shopping. H&M offers brilliant value but runs small—I usually size up, especially in their fitted styles. Their Conscious range in organic cotton is particularly good. Zara is my go-to for fashion-forward cuts, though their sizing can be erratic between different lines; their Basic range is more reliable than their TRF collection.

COS deserves special mention—their T-shirts are beautifully made with a minimalist aesthetic, though they run quite boxy and oversized. If you want a relaxed fit, stick to your usual size; for a more fitted look, size down. Whistles creates lovely elevated basics with thoughtful details, and their sizing is fairly true to UK standard, though they're cut for a longer torso.

For classic, reliable fits, I rate M&S highly—their Pure Cotton range is consistent across seasons, and they offer petite, regular, and tall lengths. Jigsaw produces quality basics with an artistic edge, cutting slightly generously through the body. Reiss sits at the premium end of the high street with sophisticated, well-cut tees that justify the price point—they fit true to size with a contemporary, tailored feel.

Don't overlook The White Company, particularly for luxurious basics in beautiful fabrics. Their sizing is generous and perfect for a relaxed, elegant look. If you're after sports-inspired tees, Lululemon offers technical fabrics with precise sizing—their size charts are incredibly accurate, and the quality is exceptional.

Premium Picks Worth the Investment

When you're ready to invest, Me&Em creates beautifully designed everyday pieces with an emphasis on fit. Their T-shirts are cut to flatter, with thoughtful details like sleeve length and neckline depth. Expect to pay £65-95, but the quality and fit consistency make them wardrobe staples. Claudie Pierlot, a French brand with a Parisian sensibility, offers chic basics that run small—always check their size guide as their "M" is more like a UK 10.

Luxury and Designer Options

If budget allows, Max Mara produces exquisite T-shirts in premium fabrics with impeccable construction. Their sizing is Italian, so runs smaller than UK sizing. For contemporary luxury, Totême creates architectural, minimalist pieces that have become cult favourites—their T-shirts are investment pieces with distinctive cuts. The Row offers the ultimate in understated luxury with perfect proportions, though expect to pay £200+ for what is essentially a perfectly made white tee.

My Styling Tips for T-Shirt Shopping

Always check the fabric composition—100% cotton will shrink slightly after washing, whilst cotton-modal blends maintain their shape better. Look for sleeve length details: cap sleeves suit petite frames, whilst longer sleeves balance broader shoulders. For a universally flattering fit, I recommend a crew neck that sits just below the collarbone and sleeves that end mid-bicep.

Consider your body shape: if you're curvier, avoid ultra-slim fits in stretchy fabrics that cling. Instead, opt for structured cotton in a relaxed fit. If you're straight through the body, fitted styles in jersey work beautifully. Pay attention to length too—cropped tees suit high-waisted bottoms, whilst longer lengths are ideal for tucking.

Two Brands You Might Not Know

Colorful Standard is a Scandinavian brand creating sustainable basics in organic cotton with exceptional colour ranges. Their sizing is precise and European-leaning. Kowtow, a New Zealand brand using Fair Trade organic cotton, produces ethically made T-shirts with a relaxed fit and beautiful drape—their sizing runs slightly generous.

Never Guess Your Size Again with Tellar

This is exactly why I recommend Tellar.co.uk—the UK's leading sizing tool that matches your body to over 1,500 brands instantly. No more guessing whether you're a 10 or 12, no more returns because the fit is wrong.

Here's how it works:

1. Measure once using your bust, waist, and hip measurements, or simply input a size from a brand that fits you perfectly. The Store Size Lookup tool then translates this across every brand—whether you're shopping at COS, Reiss, Mango, or anywhere else.

2. Get your precise size instantly in any brand you're browsing. Shopping at Zara? Tellar tells you your exact size. Trying COS? Tellar has you covered. It's like having a personal sizing assistant for every single brand.

3. It's completely free and works directly in your browser—no apps to download, no subscriptions, just instant, accurate sizing information whenever you need it.

Tellar Fashion Hub: Your Free Styling Resource

Beyond sizing, Tellar offers a comprehensive Fashion Hub—a library packed with free posts from experienced stylists like me. We cover every fashion query you can think of, always honest, unbiased, and independent. No sponsored content, no hidden agendas, just genuine style advice.

Dive into guides like The Ultimate Clothing Sizing Guide for more insights on navigating different brands. Planning your denim wardrobe? Check out Jean Trends 2026. Need help with dresses? Our Ultimate Guide to Dresses covers styles, body shapes, and where to shop. There's also an Ultimate Guide to Jackets to help you find your perfect fit.

The best part? It's all free, forever. No size guides to squint at, no returns because you guessed wrong, no frustration. Just confident shopping across every brand you love. Head to Tellar.co.uk and transform how you shop for T-shirts—and everything else.