What Is Sizing Like at Cotton On?

BY ELLA BLAKE — FASHION STYLIST | TELLAR FASHION HUB

Cotton On is an Australian fashion retailer founded in Geelong, Victoria in 1991, now operating across more than 20 countries worldwide with a range covering womenswear, menswear, activewear, loungewear, and basics.

I'll be honest — Cotton On is one of those brands I first discovered on a trip to Sydney, bought a pile of basics that I absolutely loved, and then came home to the UK and completely failed to reorder the right size online. Twice. It's not that the brand is wildly inconsistent, it's that their Australian sizing trips people up when they're shopping from the UK, and certain categories run noticeably smaller than what you'd expect from a typical high street store. So let me save you the headache — and the return shipping costs.

How Does Cotton On Sizing Work?

Cotton On uses Australian sizing, which on paper lines up with UK sizing — an AU 10 is a UK 10, an AU 12 is a UK 12, and so on. So far, so straightforward. The complication is that Cotton On's actual garment measurements tend to run on the smaller side compared to your typical UK high street sizing. Think of it like this: you might be a confident size 10 in Marks & Spencer or Next, but in Cotton On you could find yourself reaching for a 12, particularly in fitted styles and their denim.

The other thing worth knowing is that Cotton On's range extends from XS/XXS right up to a size 20 in many categories, though extended sizing availability varies by garment type. If you're shopping for Cotton On Body — their intimates and lounge basics line — sizing tends to be more consistent, which is a relief given how popular that range is.

Ella's tip: Before ordering Cotton On online from the UK, punch your measurements into Tellar's Store Size Lookup to get your exact size. Returns from Australia can be a pain — better to get it right first time.

Cotton On Size Conversion Chart

Here's how Cotton On's AU sizing maps across to UK, EU, and US equivalents — useful for cross-referencing with other brands in your wardrobe.

COTTON ON / AUUK SIZEEU SIZEUS SIZELABEL44320XXS66342XS88364XS–S1010386S1212408M14144210L16164412XL18184614XXL20204816XXXL

Body Measurement Guide

If you're shopping online and want to match your measurements directly, here's Cotton On's women's body measurement guide. When in doubt between two sizes, Cotton On themselves recommend sizing up.

SIZE (AU/UK)BUST (CM)WAIST (CM)HIPS (CM)6 / XS80–8460–6486–908 / XS–S84–8864–6890–9410 / S88–9368–7394–9812 / M93–9873–7898–10314 / L98–10378–83103–10816 / XL103–10883–88108–11318 / XXL108–11388–93113–118

Jeans & Denim

This is where Cotton On catches the most people out. Their jeans — whether you're looking at the Straight Leg, Mom Jean, 90s Baggy, or Low Rise styles — tend to run small at the waist. The leg length and hip measurements are usually fine, but the waistband is noticeably fitted. I learned this the hard way when I ordered my usual size and couldn't do up the button on a pair of their low-rise straight-leg jeans. A size up and they fit perfectly — longer in the leg than I expected, but that's easily sorted.

If you're between sizes — always size up in Cotton On denim.
If you have a fuller seat or hips — go up one, possibly two sizes at the waist; the fabric has very little stretch in most styles.
Petite shoppers — the leg length is generous, so budget for a hem.

Tops, T-Shirts & Basics

Cotton On's basics range — their cropped tees, oversized shirts, graphic tees and tank tops — is honestly one of the things I think they do really well. Sizing here is generally much more straightforward. Most relaxed-fit styles are true to size, and the oversized pieces are genuinely oversized (not that annoying "fashion oversized" that's only barely bigger than a regular fit).

Fitted tops & bodycon styles — size up if you're fuller on the bust; the fabric can pull.
Oversized and relaxed styles — true to size or size down if you want a more cropped look.
Cropped tees — true to size; the crop hits around the navel on most heights.

Dresses

Cotton On's dress range is broader than people give it credit for — they do everything from jersey midi dresses and wrap styles to printed tea dresses and mini slip dresses. The fit really depends on the fabric and cut.

Jersey and ribbed dresses — these are forgiving and usually true to size; the stretch compensates for any minor size differences.
Wrap dresses and structured styles — size up if you carry any weight in your waist or chest; these can pull across the front.
Slip and satin-finish dresses — true to size but cut close to the body; size up for a more relaxed drape.

Loungewear & Cotton On Body

The Cotton On Body range — leggings, bralettes, sports bras, ribbed sets — is genuinely one of their strongest categories. The quality-to-price ratio is excellent, and sizing here is the most consistent across the whole brand. Most pieces are true to size.

Leggings — true to size; the waistbands are comfortable and hold well.
Bralettes and soft bras — best suited to A–C cups at size; DD+ wearers may want to size up or look for styles with adjustable straps for extra support.
Ribbed lounge sets — true to size; generous enough in the hip to be comfortable all day.

Swimwear

Cotton On's swimwear looks gorgeous — lots of colourful prints and flattering cuts — but I'd be doing you a disservice if I didn't flag that it runs small, especially across the bust. The designs are cut for a more petite silhouette, so if you have a fuller bust or want proper coverage, go up at least one size.

Fuller bust (DD+) — size up; the cups are on the small side across the whole swim range.
High-waist bottoms — can run small at the waist; size up if you're between sizes.
Bikini tops — consider sizing the top and bottom separately for a better fit overall.

If Cotton On Doesn't Quite Work for You — Try These Instead

Cotton On is brilliant for affordable basics and casual everyday wear, but if the sizing isn't working in your favour or you can't get your hands on it easily in the UK, these alternatives cover a very similar aesthetic and price point:

High Street Picks

H&M — probably the closest UK equivalent; easy-to-find basics, casual tees, and loungewear with consistent sizing and a similar relaxed aesthetic.
Monki — great for the same laid-back, casual-cool vibe; slightly more playful but excellent for basics and denim.
Weekday — slightly more elevated basics with a Scandi edge; sizing is clear and consistent, and their denim is excellent.
Bershka — if you love Cotton On's trendier pieces (the low-rise jeans, the graphic tees), Bershka covers similar ground at a very similar price point.
Pull & Bear — a solid go-to for casual everyday basics, oversized tees, and comfy lounge styles; sizing runs true to UK high street standard.
New Look — reliable for the casual basics category; sizing is consistent and their extended size range is excellent.
Primark — for the super-affordable end of the basics market, Primark is hard to beat; UK sizing is very straightforward here.

Independent & Niche Picks

Colorful Standard — if what you love about Cotton On is the clean basics in great colours, Colorful Standard does exactly that in sustainable fabrics and with proper size guidance. A step up in price but genuinely worth it for core wardrobe pieces.
Lucy & Yak — a brilliant UK-based independent brand for casual, comfortable everyday dressing with brilliant sizing transparency and a really honest, body-positive approach to fit. Their dungarees and wide-leg styles are iconic for a reason.

Premium & Luxury Alternatives

COS — for elevated, clean-line basics with a more architectural feel; sizing is generous and consistent, and the quality is a big step up.
Sézane — if you want the casual-chic feel of Cotton On's better pieces but with a Parisian finish and longevity, Sézane delivers beautifully; their size guides are very detailed.
& Other Stories — excellent for the dresses and tops category in particular; slightly more considered design than the high street with reliable sizing across the range.

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