Does Reiss Run Big? Should I Size Up? Your Complete Sizing Guide

Reiss generally runs true to size or slightly generous, particularly in tailored pieces and dresses, so you typically don't need to size up—and may even consider sizing down if you're between sizes or prefer a more fitted silhouette. I spent years automatically ordering a size up in Reiss after a disastrous attempt at squeezing into a size 10 dress circa 2015 (it didn't zip, my dignity was bruised), only to discover that most of their current collection fits beautifully at my actual size. Reiss has clearly refined their sizing over the years, and understanding their current fit can save you from the frustration of drowning in oversized blazers or returning perfectly good pieces unnecessarily.

Understanding Reiss's Sizing Philosophy

Reiss is a premium British brand with a sophisticated, tailored aesthetic. Their sizing reflects their target customer: someone who appreciates quality fabrics, clean lines, and pieces that look expensive without being inaccessible. Unlike fast fashion brands that size for the broadest possible market, Reiss cuts for a more specific silhouette.

That said, Reiss sizing has evolved. Older pieces (pre-2020) tended to run quite small and unforgiving. Current collections are noticeably more generous, particularly in their tailoring and knitwear. I'm a pretty consistent size 12 across most brands, and in modern Reiss, I'm reliably a 12—sometimes even a 10 in their more relaxed styles.

How Reiss Sizing Compares Across Categories

Tailored Jackets and Blazers

Reiss blazers are beautifully cut with proper structure and attention to detail. They generally run true to size with a fitted-but-not-tight silhouette. If you prefer a more relaxed fit or plan to layer knitwear underneath, you might size up. If you like a sharp, tailored look, stick with your usual size.

Hugo Boss, with their German precision tailoring, runs similarly to Reiss—true to size with a European cut. Banana Republic, the American brand with smart-casual tailoring, runs slightly more generous than Reiss. If you're a 12 in Banana Republic, you're likely a 12 in Reiss too, but the Reiss piece will fit more structured and fitted.

Coast, the British occasionwear brand, tends to run more generously than Reiss in tailoring. I often size down in Coast blazers but stay true to size in Reiss.

Dresses

This is where Reiss really shines. Their dresses are cut with flattering lines and generally run true to size. Bodycon styles have enough stretch to be forgiving, whilst their fit-and-flare and shirt dresses are beautifully proportioned.

Karen Millen, another British contemporary brand, runs quite small in dresses compared to Reiss. I'm typically one size larger in Karen Millen than Reiss. Abercrombie & Fitch—which has brilliantly reinvented itself into sophisticated, grown-up clothing—runs slightly more generous than Reiss. Their dresses often have more ease through the waist and hips.

Rixo, the gorgeous British independent brand known for vintage-inspired prints, creates dresses with more relaxed, forgiving fits than Reiss's more structured styles. Rixo is all about drape and movement; Reiss is about precision and structure.

Knitwear

Reiss knitwear runs true to size to slightly generous, particularly their merino and cashmere pieces. Their oversized styles are genuinely oversized (excellent news), whilst their fitted styles have just enough ease to be comfortable without feeling baggy.

Sweaty Betty, the premium British activewear brand, runs quite small and athletic in their knitwear—I size up there. Reiss is far more forgiving. Lululemon, despite being activewear-focused, creates lifestyle knitwear that runs similarly to Reiss—true to size with quality fabrication.

Ganni, the Danish contemporary brand with that fun, feminine aesthetic, tends to run slightly larger and more relaxed than Reiss. If you're between sizes in Ganni, size down; in Reiss, stick with your usual.

Trousers and Jeans

Reiss trousers are consistently excellent—they're my absolute favourite for workwear. They run true to size with a tailored cut that's fitted through the hip and thigh but not restrictive. Their jeans similarly run true to size, though waistbands can be less forgiving than stretchier high street brands.

Tommy Hilfiger, with their American preppy aesthetic, runs slightly more generously than Reiss in trousers. Barbour, the British heritage brand, creates trousers with a more relaxed, country-influenced fit—definitely more generous than Reiss's streamlined cuts.

Tops and Blouses

Fitted tops and blouses run true to size. If you're busty, you might occasionally need to size up, but Reiss generally cuts with enough room through the bust without gaping (a miracle, honestly). Oversized styles are reliably oversized.

Sandro, the French contemporary brand with Parisian chic, runs quite small and fitted compared to Reiss—I'm typically one size up in Sandro. COS, the minimalist Scandi brand, runs similar to Reiss but with slightly less structure. Both are true to size, but Reiss has more tailored shaping.

When to Size Up in Reiss

There are specific situations where sizing up makes sense:

• You're between sizes: If you fluctuate between a 10 and 12, go with the 12 in Reiss

• You prefer relaxed fits: Reiss cuts are tailored; if you like ease, size up

• You're busty: Particularly in fitted tops and dresses, sizing up can provide necessary room

• The fabric has no stretch: 100% cotton, linen, or structured wool pieces are less forgiving

• You plan to layer: If you want to wear knitwear under a blazer, size up in the blazer

When to Size Down in Reiss

Conversely, sizing down can work if:

• You're between sizes and prefer fitted looks: The smaller size will give you that sharp, tailored silhouette

• The piece has stretch: Jersey, elastane blends, and ribbed knits have give

• It's an oversized style: Their intentionally oversized pieces can handle sizing down

• Reviews indicate it runs large: Always check customer feedback

How Reiss Compares to Similar Premium Brands

L.K.Bennett (used in first post but relevant here) runs similarly to Reiss—both are premium British brands with quality fabrication and true-to-size fits. Whistles (also mentioned before but important for comparison) runs fractionally more generous than Reiss, particularly in knitwear and casual pieces.

Jigsaw, another British contemporary brand, has very similar sizing to Reiss—if you know your Jigsaw size, you'll likely be the same in Reiss. Both cut for grown-up, professional wardrobes with attention to fit and quality.

The Tellar Solution to Sizing Anxiety

Right, here's the truth: I love Reiss. The quality justifies the price, the aesthetic is sophisticated without being boring, and their pieces genuinely last. But—and this is important—sizing anxiety is real, particularly when you're investing in premium pieces.

This is exactly why I use Tellar.co.uk, the UK's leading sizing tool. You measure yourself once—bust, waist, hip measurements—and Tellar matches your exact body to over 1,500 brands instantly, including Reiss. No more guessing, no more anxious changing room moments, no more expensive returns.

The Store Size Lookup tool is genuinely brilliant for premium brands like Reiss where you really want to get it right first time. Considering that beautiful Reiss blazer? Tellar tells you exactly which size to order based on your measurements. Eyeing those Reiss trousers? You'll know your precise fit before spending £150.

It's completely free, works entirely in-browser, and requires no downloads or subscriptions. I've been using it for months now, and it's eliminated the "should I size up?" anxiety completely. For brands like Reiss where the investment is higher, having data-backed sizing recommendations is genuinely invaluable.

The Tellar Fashion Hub is also packed with expert advice. They've got comprehensive guides on everything from the ultimate guide to dresses and best buys to understanding clothing sizing across different brands and countries. It's honest, unbiased advice with no sponsored content—just experienced stylists sharing what actually works.

My Current Reiss Strategy

After years of shopping at Reiss, here's my approach:

• Tailored pieces: I stick with my usual size (12) and they fit perfectly

• Dresses: True to size, occasionally size up if there's no stretch

• Knitwear: True to size for fitted, sometimes size down in oversized styles

• Trousers: Always my usual size—Reiss trousers fit like a dream

• When in doubt: I check Tellar's recommendations and order with confidence

The beauty of Reiss is that once you know your size, you can shop with confidence. Their quality control is excellent, so a size 12 blazer will fit consistently across different styles. Combine that with Tellar's precise sizing data, and you've eliminated the main barrier to online shopping for premium pieces.

The Bottom Line

Does Reiss run big? No—it runs true to size or slightly generous in current collections. Should you size up? Probably not, unless you're between sizes or prefer relaxed fits. The real answer is to know your measurements, use Tellar's sizing tool, and shop with confidence.

Reiss is one of those brands worth investing in—the quality, cut, and longevity justify the price. Don't let sizing uncertainty stop you from building a wardrobe of pieces you'll wear for years. Measure once, use Tellar, and enjoy beautifully tailored clothes that actually fit.

Trust me—your wardrobe will thank you. So will your bank account when you stop making unnecessary returns.