Should I Size Up for Jackets and Coats?

The short answer is: it depends on the style, fabric, and how you plan to layer underneath. As a stylist who's spent years helping clients navigate the confusing world of outerwear sizing, I can tell you that this is one of the most common questions I hear every autumn. I've made my fair share of mistakes—I once bought a gorgeous wool coat in my usual size, only to realise I couldn't comfortably wear a chunky knit underneath. That £200 lesson taught me to think strategically about coat sizing, and I'm here to save you from the same fate.

Understanding Your Coat's Purpose

Before you even think about sizing, ask yourself: what will you be wearing underneath? A lightweight spring jacket over a T-shirt has completely different requirements to a winter coat that needs to accommodate thick jumpers and scarves. I always tell clients to consider their actual wardrobe, not some idealised capsule wardrobe from Pinterest.

For blazers and structured jackets that you'll wear over blouses or thin knits, stick to your true size. These are designed to skim your body with just enough room for movement. Sizing up will make the shoulders droop and the sleeves bunch awkwardly at your wrists—never a good look.

However, for proper winter coats, puffer jackets, and oversized styles, sizing up is often the smarter choice. You need that extra breathing room for layering, plus the relaxed fit is actually more flattering on most body types. I learned this the hard way when I squeezed into a 'true to size' puffer that made me look like a stuffed sausage. Not cute.

Fabric Matters More Than You Think

Stiff fabrics like wool, leather, and structured cotton have zero give. If you're between sizes, always go up with these materials. I remember trying on a leather biker jacket at All Saints—their edgy cuts and premium leather make for investment pieces that'll last years—but I initially chose my usual size 10. I could barely lift my arms. The size 12 was perfect: still fitted but actually wearable.

Conversely, soft fabrics with stretch—think jersey, knit coats, or anything with elastane—are more forgiving. Cos does brilliant minimalist coats in these fabrics, and Uniqlo (yes, they do womenswear brilliantly despite being less talked about) excels at stretchy, packable outerwear that fits true to size.

High Street Heroes for Every Budget

When shopping high street, certain brands consistently nail coat sizing. Zara tends to run quite fitted, so I always size up for their outerwear—their trendy oversized coats are having a moment right now, and the extra room makes them infinitely more practical. Mango is my go-to for mid-weight coats that feel expensive; their sizing is generous enough that you can usually stick to your normal size even with layering.

H&M offers incredible value, though quality can be hit-or-miss. Check the fabric composition religiously. M&S is underrated for classic wool coats—their sizing runs traditional (slightly larger than European brands), making them perfect for British winters where you actually need to wear clothes underneath.

For something different, try Arket (sister brand to Cos, with Scandinavian minimalism and excellent quality) or Everlane (American brand but ships to UK, famous for transparent pricing and timeless designs). Both offer beautifully cut coats that layer brilliantly.

Premium Picks Worth the Investment

Reiss makes stunning tailored coats that run true to size, but their structured styles aren't designed for heavy layering. If you want to wear thick knits underneath, absolutely size up. Whistles is my secret weapon for contemporary cuts that feel fashion-forward without being trendy—their sizing is consistent, and their coats actually accommodate real bodies.

Me&Em has perfected the art of elevated basics. Their coats are pricey but the fit is impeccable, designed by women who actually understand how we dress. LK Bennett offers classic styles with a modern twist, though their sizing can run slightly small, particularly in the shoulders.

Luxury Options for Coat Lovers

If you're investing in a designer coat, try before you buy or check return policies religiously. Max Mara is the holy grail of wool coats—yes, they're expensive, but they last decades. Their iconic styles run true to size, but allow for some layering. Jil Sander creates sculptural, oversized silhouettes that are deliberately roomy (think fashion-editor chic), so stick to your usual size or you'll drown.

The Puffer Jacket Exception

Puffers are a category unto themselves. The quilted construction means they need extra room to move without restricting. Superdry does affordable puffers that run true to size but are already generously cut. The North Face (another brilliant but often overlooked option for women's outerwear) sizes their technical jackets with layering in mind, so stick to your usual size.

For cropped puffers, Zara and Bershka lead the high street. These shorter styles can handle your true size since they don't need to close over thick jumpers. Think of them as statement pieces, not practical winter armour.

My Professional Sizing Strategy

Here's what I tell every client:

• Try with layers: Bring a chunky knit to the fitting room. Seriously. It changes everything.

• Check the shoulder seams: They should sit at your natural shoulder point, not drooping down your arms or pulling up towards your neck.

• Lift your arms: Can you move freely? If not, size up.

• Button it closed: Is there pulling or gaping? That's your cue to adjust sizing.

• Consider alterations: Sometimes buying the larger size and having sleeves shortened is smarter than squeezing into a smaller size.

Brand-Specific Quirks to Know

French Connection tends to run small in outerwear despite their size charts suggesting otherwise. Always size up. Jigsaw is more generous, particularly in their relaxed styles. Massimo Dutti (Zara's sophisticated older sister) offers better quality but similar sizing—expect fitted cuts that need sizing up for layering.

I'm obsessed with Rains for waterproof coats that actually look good—their unisex sizing runs large, so women often size down. But if you want an oversized, Scandi vibe, stick to your usual size.

Never Look at a Size Guide Again with Tellar

Here's the thing that changed my entire approach to online shopping: I discovered Tellar.co.uk, the UK's leading sizing tool. Instead of playing Russian roulette with sizing charts, you measure once—bust, waist, hip, or use your existing brand size—and Tellar matches your body to over 1,500 brands instantly.

Their Store Size Lookup tool is genuinely life-changing. Want to know your exact size in Cos, Reiss, Everlane, or Arket? Type in your measurements once, and Tellar tells you precisely what to order. No more ordering three sizes and dealing with returns. No more guessing.

It's completely free, works in your browser (no downloads), and has saved me countless returns. As someone who orders coats online constantly for clients, this tool has become absolutely essential to my work.

Tellar's Fashion Hub: Your Style Encyclopedia

Beyond sizing, Tellar's Fashion Hub is stacked with honest, unbiased posts from stylists like me. No brand partnerships influencing recommendations—just real advice. They cover everything from jeans trends for 2026 to the ultimate guide to dresses.

Their comprehensive jacket guide goes even deeper into styles, body shape matching, and brand comparisons. Plus, their ultimate clothing sizing guide explains why sizing is such chaos in the first place—fascinating reading if you're a fashion nerd like me.

Final Verdict

Should you size up for jackets and coats? Usually yes for outerwear designed for layering, sometimes for structured jackets depending on fit, and definitely check brand-specific quirks before committing. The smarter approach? Use Tellar to take the guesswork out entirely. Your wardrobe (and your sanity) will thank you.