ASOS Size Guide: What Size Am I in ASOS? UK Sizing Help & Brand-by-Brand Fit Comparison

Online Fashion Fit Breakdown | Tellar.co.uk

Affordable, On-Trend, and Global — But Does ASOS Sizing Run Big or Small?

ASOS is the UK’s biggest online fashion destination, offering everything from Y2K festivalwear to sharp tailoring and high-street basics. It’s known for trend-led edits, extended sizing, and a broad catalogue of brands — including its own in-house labels like ASOS Design, Collusion, and ASOS Edition.

But with so many brands, fits and silhouettes under one digital roof, sizing can feel inconsistent.

What size am I in ASOS? And how does sizing differ between their in-house brands and the other labels they sell?

Want to get your exact ASOS fit instantly?

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Does ASOS Run Big or Small?

ASOS in-house brands tend to run true to size overall, but with variations depending on fabric, silhouette and sub-label.

Here’s what we’ve found across categories:

ASOS Design = true to size in most styles, but slim-fitting in tailored or occasion pieces
Collusion = gender-neutral, often oversized — size down for a fitted silhouette
ASOS Luxe / Edition = elevated, structured fits — many pieces run small
Marketplace brands (e.g. vintage reworks, boutique labels) = variable — always check size guides
Third-party brands (like Pull&Bear, Bershka, New Look) follow their own size systems, even when sold through ASOS

🎯 Tellar takes your measurements and matches them to ASOS and every brand they stock

Quick UK Sizing Conversion (ASOS Core Fit)

UK Size	ASOS Label	Notes
UK 6	XXS	Slim fit, especially in tailoring
UK 8	XS	True to size in casualwear
UK 10	S	Comfortable for most builds
UK 12	M	Size up in occasion dresses
UK 14	L	Great in oversized pieces
UK 16–18	XL–XXL	Available across most in-house ranges

ASOS Sizing by In-House Brand

✦ ASOS Design

The main line — covers everything from basics to suits to bridalwear.

Casualwear and denim = true to size
Tailoring and formal = may run small, especially around the bust and waist
Maternity & Curve = extended sizing with adjusted proportions — check rise and length if you’re petite

✦ Collusion

Gender-neutral label with streetwear roots.

Sweatshirts, joggers, tees = oversized by default
Trousers and outerwear = relaxed cut — size down for structure
Petite and tall ranges available, though inseams can still vary

✦ ASOS Luxe / ASOS Edition

Premium capsules with designer-inspired silhouettes and occasion-ready detail.

Dresses and suits = run small, especially if structured or zip-back
Size up in anything woven, pleated or corset-style

✦ ASOS 4505 (Activewear)

ASOS’s sportswear range, spanning leggings, crop tops and layering pieces.

Leggings = true to size, mid- to high-rise
Tops = close cut — size up if you prefer a relaxed fit

📏 Not sure of your body measurements? Download your free Tellar measuring tape and set up your profile now.

Third-Party Brand Sizing on ASOS

ASOS also stocks hundreds of external brands — and many follow different sizing conventions. Here's how some of the most popular compare:

Brand	Fit vs ASOS Design	Notes
Pull&Bear	Smaller	Size up in jeans and blazers
Bershka	Smaller	Especially snug in dresses and tops
Stradivarius	Smaller	Slim hip and chest fit
New Look	Similar	True to size overall
Topshop (via ASOS)	Slightly smaller	Especially in trousers and jackets
Monki	Larger	Generous cuts and wide waists
Weekday	Variable	True to size in basics, oversized in tops
Never Fully Dressed	Smaller	Size up in dresses

🎯 Tellar instantly adjusts for brand-to-brand fit differences, so you always get the right size

Fit Feedback From Tellar Users

Item Type	Runs Small	True to Size	Runs Large
ASOS Design Occasionwear	✅	✅
Collusion Hoodies		✅	✅
Topshop Jeans via ASOS	✅	✅
ASOS 4505 Leggings		✅
Pull&Bear Dresses	✅	✅

Looking for help with other brands on ASOS? Try these guides from Tellar:

Topshop sizing guide
Pull&Bear sizing explained
Bershka fit help
Stradivarius size advice
Monki sizing tips

Smart Pieces to Try from ASOS

✔ ASOS Design Jeans

Consistently rated true to size. Choose based on rise and cut — skinny and straight-leg styles are snug at first wear.

✔ ASOS Luxe Blazer Dresses

Size up for comfort across the chest and arms. Stunning tailoring with a slim cut.

✔ Collusion Jogger Sets

Great for casualwear. Oversized by default — size down if you're petite or prefer a closer fit.

✔ ASOS 4505 Activewear

Leggings and crop tops run true to size. Support levels vary — check product description before buying.

🛍 Tellar matches your fit across every ASOS label and the brands they stock

Practical Tips Before You Order

Check fabric notes and stretch levels — woven = fitted, jersey = forgiving
If a product says “bodycon” or “structured” — size up unless you like a snug fit
In-between sizes? Go with the larger if ordering tailoring or outerwear
Use Tellar to avoid multiple returns and know exactly what you’re getting

Why Tellar Helps You Shop ASOS Smarter

Between ASOS’s own labels, dozens of stock brands, and endless trends, sizing isn’t always straightforward. Tellar helps you make smarter decisions before you hit “add to basket” by:

Matching your size to thousands of brands
Converting between UK, EU and US sizing
Factoring in style, stretch and garment type
Giving you a real-world fit match in under a minute

Create your Tellar profile now and take the uncertainty out of online shopping

Ready to Find Your ASOS Size?

Let Tellar do the work. We’ll match your measurements to ASOS and every other brand you shop — instantly and accurately.

Create your free Tellar profile
Check your ASOS size across labels and brands
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