Does ASOS Run Small? Should I Size Up? Your Complete ASOS Sizing Guide

ASOS sizing varies dramatically because they stock over 850 different brands alongside their own-brand ranges - ASOS Design runs relatively true to size with a relaxed fit, whilst ASOS Petite and Tall adjust proportions not just length, but brands like Topshop, River Island, and New Look sold on ASOS each have completely different sizing standards - meaning you could genuinely need three different sizes in three different items from the same ASOS order. I learnt this the expensive way when I ordered five dresses for a holiday, all in my usual size 12, and ended up with one that was massive, two that were perfect, one that was tight, and one I couldn't even zip up. The return label situation was not fun!

Understanding the ASOS Sizing Puzzle

Here's what makes ASOS uniquely complicated: they're a marketplace as much as a retailer. When you buy "ASOS Design", you're getting ASOS's own-brand clothing with their sizing standards. When you buy Topshop (now exclusive to ASOS), you're getting Topshop sizing which runs small. When you buy New Look on ASOS, you get New Look's sizing which runs more generous. It's like shopping in ten different shops simultaneously.

The frustration is real - you can't develop an "ASOS size" the way you might have a "Zara size" or an "M&S size". Every brand on the platform has its own sizing philosophy, and ASOS doesn't standardize them. This is why so many people ask if ASOS runs small - the answer is: it depends entirely on which brand you're buying.

Breaking Down ASOS Own-Brand Sizing

ASOS Design: The Main Range

ASOS Design generally runs true to size with a slightly relaxed, contemporary fit. Their sizing is more generous than Topshop (which runs small) and more fitted than Monki (which runs quite large). I'd say it's similar to H&M sizing - relatively consistent but with variation between different product categories.

Their jeans tend to run true to size with good stretch. Ridley skinnies are consistently sized, whilst their wide-leg styles are more generous. Dresses can be hit-or-miss - bodycon styles run small, whilst oversized or shift dresses run large. It's not rocket science, but it does require reading the product description carefully.

ASOS Petite, Tall, and Curve

This is where ASOS actually excels. Their Petite range doesn't just shorten lengths - they adjust sleeve lengths, rises, and overall proportions. Same with Tall - they lengthen the body, not just the hem. Curve (UK 18-30) is designed for curvier body shapes with adjusted bust, waist, and hip measurements.

Compare this to Next where Petite often just means shorter legs, or M&S where Tall sometimes feels like regular sizing with longer hems tacked on. ASOS actually rethinks the entire pattern, which is brilliant.

ASOS Edition and Premium Lines

ASOS Edition (their occasionwear) tends to run smaller and more fitted than regular ASOS Design. Think Coast or Phase Eight sizing - designed to be body-conscious. I always size up in ASOS Edition dresses because they're cut for a very fitted silhouette.

The Third-Party Brand Minefield

Brands That Run Small on ASOS

Topshop (now ASOS exclusive) runs notoriously small. The Joni jeans, Jamie jeans, all of it - size up at least one, sometimes two. Their dresses are designed for a slim, young fit. I'm always one size up in Topshop compared to ASOS Design.

River Island on ASOS has the same sizing issues as buying direct - runs small across most categories, particularly in fitted dresses and the Molly jean range. Size up one if you're between sizes.

Urban Outfitters brands (BDG, Silence + Noise) run very small with a US sizing influence. What they call a UK 12 often fits more like a UK 10. Always check the actual measurements.

Brands That Run True to Size

New Look on ASOS runs relatively true to size and slightly generous - similar to high street standards. Their sizing is more forgiving than Topshop or River Island.

Monki runs true to size or slightly large with a relaxed, Scandi aesthetic. Their sizing is more generous than average - I sometimes size down in Monki oversized pieces.

Weekday (another Scandi brand) runs true to size with a contemporary, relaxed fit. Similar sizing philosophy to COS - generous and modern.

Premium Brands on ASOS

French Connection has improved their sizing consistency and now runs relatively true to size. Whistles pieces on ASOS run true to size with a sophisticated, slightly generous fit. Gant runs quite generous - classic American sizing that's roomier than British brands.

When you venture into premium territory like Calvin Klein or Tommy Hilfiger on ASOS, you're dealing with more standardized, international sizing that tends to run true to size or slightly generous.

The Independent Brands to Know

Ghospell is an independent brand on ASOS creating gorgeous, contemporary pieces with excellent sizing consistency. They run true to size with detailed size guides, and their aesthetic is fresh and modern. I've never had a sizing issue with Ghospell - what the measurements say is what you get.

COLLUSION is ASOS's sustainable, unisex brand designed in collaboration with influencers and customers. The sizing is intentionally relaxed and oversized, with detailed measurements for every piece. They're transparent about fit, which makes shopping them so much easier than guessing with other brands.

How to Navigate ASOS Sizing Successfully

The Essential Strategy:

• Never assume your size is consistent across different brands on ASOS

• Always check which brand you're buying - ASOS Design vs Topshop vs River Island

• Read the size guide for every single item - they're brand-specific

• Check the actual garment measurements, not just the size chart

• Read reviews religiously - ASOS customers are brutally honest about sizing

Reading Reviews Like a Pro:

• Filter reviews by your height and usual size

• Look for phrases like "runs small", "size up", "tight fit"

• Check what size reviewers normally wear vs what they ordered

• Pay attention to comments about specific areas (bust, shoulders, length)

• If multiple reviews say "runs small", believe them!

The Fabric Factor:

• Stretch fabrics (with elastane): Usually more forgiving

• 100% cotton or linen: No give - size up if between sizes

• Polyester jersey: Can be hit or miss - check reviews

• Structured fabrics: Tend to run smaller with less room for error

When to Definitely Size Up on ASOS

Always Size Up When Buying:

• Topshop anything - seriously, just size up automatically

• River Island fitted styles

• ASOS Edition occasionwear

• Urban Outfitters brands

• Any item with reviews saying "runs small"

• Fitted or bodycon styles in any brand

• You're between sizes

Stick to Your Usual Size For:

• ASOS Design regular fit items

• New Look and Monki

• Oversized or relaxed fit styles

• Brands with stretch fabrics

• Items where reviews confirm true-to-size fit

The Game-Changing Solution

This is exactly why Tellar.co.uk is absolutely essential for ASOS shopping. You measure yourself once - bust, waist, hip - and Tellar shows you your exact size across all 850+ brands that ASOS stocks. Topshop size? Sorted. River Island size? Done. ASOS Design size? Got it.

The Store Size Lookup is genuinely life-changing for ASOS shopping. Instead of guessing whether you need a 10, 12, or 14 based on which brand you're buying, Tellar tells you exactly which size to order based on your actual measurements. It's completely free, works in your browser instantly, and has saved me from countless ASOS return disasters.

My Personal ASOS Sizing Strategy

After years of ASOS sizing chaos, here's what works: I use Tellar.co.uk before adding anything to my basket. I check which brand I'm buying, use Tellar to see my size in that specific brand, and then double-check the reviews. For ASOS Design, I usually stick to my Tellar-recommended size. For Topshop, I go one size up from Tellar's suggestion. For anything without reviews, I order two sizes.

I've also learned to check measurements religiously. ASOS lists them for every item, and they're usually accurate. If a dress says the bust is 90cm and my bust is 92cm, I size up regardless of what the size chart says.

Comparing ASOS to Traditional Retailers

M&S has consistent, standardized sizing across their entire range - the complete opposite of ASOS. Next is similarly consistent. Zara is like ASOS in that sizing varies, but at least it's all Zara so you can develop a "Zara size".

Mango sizing is more consistent than ASOS because it's all one brand. Same with COS, Massimo Dutti, and Reiss - when you shop one brand, you learn their sizing. ASOS's multi-brand model makes this impossible.

The Tellar Fashion Hub Advantage

The Tellar Fashion Hub is your complete library of honest, unbiased styling advice - always free, always independent. Whether you're navigating ASOS's multi-brand chaos or building your perfect wardrobe, you'll find expert guidance without the sales pitch.

Essential reads for smarter shopping:

• The Ultimate Clothing Sizing Guide - measure yourself properly once and for all

• Jeans Trends 2026 - navigate denim sizing across all the brands ASOS stocks

• Ultimate Guide to Dresses - find your perfect fit across brands

• Ultimate Guide to Jackets - master outerwear sizing

The Bottom Line

Does ASOS run small? It's the wrong question. The right question is: "Does this specific brand on ASOS run small?" Because ASOS Design runs relatively true to size, Topshop runs small, New Look runs generous, and everything else falls somewhere in between.

Should you size up? Sometimes. It depends entirely on which of the 850+ brands you're buying from. This is why ASOS can be so frustrating - there's no consistent "ASOS size" to learn.

The solution isn't to guess or to order three sizes of everything (though we've all been there). The solution is Tellar.co.uk - measure yourself once, get your exact size across every single brand that ASOS stocks, and eliminate the guesswork entirely.

ASOS is brilliant for choice, terrible for sizing consistency. But with Tellar showing you your exact size in Topshop, River Island, New Look, ASOS Design, and every other brand on the platform, you can finally shop ASOS confidently. No more sizing chaos, no more return nightmares - just the right size, first time, every time.