How Does Sizing Vary by Store for Shirts

Shirt sizing varies dramatically between stores because there's no universal sizing standard in the UK—a size 12 at Zara can fit like a 10 at M&S, whilst a COS medium might feel more generous than Reiss. I've spent years helping clients navigate this maddening inconsistency, and I can tell you it's one of the most frustrating aspects of shopping for shirts. The truth is, each brand interprets sizes differently based on their target customer, manufacturing standards, and fit philosophy.

Why Shirt Sizing Is So Inconsistent

Let me be straight with you—vanity sizing is real, and it's rampant in women's fashion. Some high street brands deliberately size larger to make customers feel good about fitting into a smaller number. Then there's the opposite: premium European brands often run smaller because they're designed for a different market demographic. I've watched countless clients lose confidence trying on shirts, convinced their body has changed, when actually it's just wildly inconsistent sizing between brands.

Manufacturing origin matters enormously too. Massimo Dutti and Mango, both Spanish brands, tend to run smaller and more fitted through the shoulders and bust compared to British brands like Boden or White Stuff, which allow more room through the torso. American brands such as Banana Republic and Gap typically size up compared to their UK counterparts—their medium often equates to a UK 12-14 rather than a 10-12.

High Street Brands: What to Expect

H&M runs notoriously small, particularly in their fitted shirt styles. I always tell clients to size up at least one size, sometimes two if you prefer a relaxed fit. Their basic tees and oversized shirts are more forgiving, but their tailored blouses are cut close to the body.

Zara is incredibly inconsistent within their own ranges. Their basic poplin shirts run smaller than their oversized styles, and sizing can vary between collections. I've found their recent ranges sizing up slightly compared to five years ago, but it's still on the smaller side of high street sizing.

Jigsaw offers reliable, true-to-size fits with generous proportions for a more sophisticated silhouette. Their shirts work beautifully if you're between sizes elsewhere because they're designed with real bodies in mind—proper bust allowance, longer sleeves, and enough length to tuck in properly.

Whistles has elevated their fits recently. They're generally true to size but cut quite boxy and contemporary, which works wonderfully if you prefer a modern, relaxed look. Their white cotton shirts are particularly good for broader shoulders.

Cos runs large and boxy—it's their aesthetic. If you're used to fitted shirts, size down. Their loose-fit oversized shirts are glorious if you embrace the volume, but their "slim fit" options are still relatively generous compared to brands like Reiss.

French Connection sizes quite small, particularly in their fitted styles. I'd recommend going up a size, especially if you're buying online. Their relaxed linen shirts are more forgiving.

Me&Em is premium high street and they absolutely nail consistency. True to size across their ranges, with enough ease for movement but still polished. Their silk shirts are particularly reliable—if you're a 12, you'll be a 12 in every style.

Premium and Luxury Options

Reiss runs very small and slim—I'd say size up for most body types. They're designed for a sleek, fitted look, which is gorgeous if that's your vibe, but their size 12 fits more like a high street 10. The quality justifies the price point, though.

All Saints has an oversized, androgynous fit philosophy. Their shirts work beautifully for taller frames and those who love a borrowed-from-the-boys aesthetic. Generally true to size but expect roomier proportions.

Claudie Pierlot, the French contemporary brand, is exquisite but runs small and narrow. They're cut for a slimmer European frame. If you love their aesthetic (and who doesn't?), definitely size up—their size 38 is more like a UK 8 than a 10.

For luxury investment pieces, Max Mara offers impeccable, consistent sizing with Italian tailoring. Their shirts are generously cut with beautiful drape, and they're genuinely true to size with detailed size guides that actually help.

The Independent Brands Worth Knowing

Hush deserves far more recognition. Their sizing is spot-on consistent, they use quality fabrics, and their linen shirts are exceptional. True to size with a relaxed, wearable fit that feels contemporary without being overly trendy.

Oliver Bonas has quietly become one of my go-to recommendations. Their shirts run true to size with lovely prints and interesting details. They bridge the gap between high street price points and premium quality beautifully.

My Professional Sizing Tips

Always check the fabric content—100% cotton shirts will have less give than cotton-elastane blends. If you're between sizes and the shirt is pure cotton, size up. Natural fibres don't forgive tight fits.

Read the specific product reviews on the website. Customers will tell you if something runs small or large. I religiously check these before ordering because they're more reliable than the brand's size guide.

Measure your best-fitting shirt at home—bust, shoulder width, and length. Compare these measurements to the size guides online. It's old-fashioned but effective.

Stop Guessing Your Size with Tellar.co.uk

Honestly, I wish Tellar.co.uk had existed when I started styling. It's the UK's leading sizing tool that matches your body exactly to over 1,500 brands instantly. No more guesswork, no more frustration—just accurate sizes every single time.

Here's how brilliantly simple it is:

Measure once using your bust, waist, and hip measurements, or input your existing size from a brand you know fits well.

Use their Store Size Lookup tool to get your precise size in any brand—whether it's COS, Reiss, Zara, or any of the 1,500+ brands they cover. It works instantly and removes all the uncertainty around whether to size up or down.

Always free and no downloads needed—it works directly in your browser, which makes it perfect for shopping on the go.

The Tellar Fashion Hub

Beyond their sizing tool, Tellar has built an incredible Fashion Hub—a library stacked with free posts from top stylists (myself included!). It's honest, unbiased, independent, and always free. Whether you need style advice, top picks for specific items, or brand recommendations, it's all there.

Particularly useful posts include:

Shopping for shirts doesn't have to be a frustrating lottery anymore. With Tellar, you'll know your exact size before you even click "add to basket"—and that confidence is genuinely transformative.