What Is Sizing Like at The Upside?

By Ella Blake — Fashion Stylist | Tellar Fashion Hub — Always honest, unbiased & unsponsored

The Upside generally runs true to size, but with a technical, body-skimming fit that means if you're between sizes or carry more volume in the hips or chest, you'll want to size up — and trust me, it's worth getting right, because on a brand at this price point, you really don't want to be guessing.

I came to The Upside a few years ago via a friend who'd returned from Sydney practically evangelical about their leggings. "They're the ones that make your legs look like they belong to someone who actually enjoys running," she said, which felt deeply relevant to me as someone who does not enjoy running. She wasn't wrong. I ordered a pair of the Ribbed flares in my usual size and they were perfect — long enough (I'm 5'8"), sculpting without being restrictive, and genuinely beautiful. Then I tried their sports bras. Sized up by one and still felt like I was being mildly compressed. The lesson? The Upside rewards a little due diligence — not a lot, just a little.

About The Upside

Founded in Sydney in 2013, The Upside is an Australian premium activewear brand that has firmly planted its flag at the intersection of fashion and function. This is not your budget gym kit. The Upside is the brand you see on well-dressed women leaving pilates studios in Notting Hill, carried over one shoulder in a tote that costs more than most people's monthly gym membership. Their pieces are designed to be worn from studio to street without changing — and they genuinely pull it off. The fabrication is exceptional, the prints are often genuinely stunning, and the silhouettes are considered in a way that most activewear simply isn't.

They use their own size labels (XXS through XL, plus some extended sizing), which broadly align with standard UK sizing — but with the snug, performance-focused fit that Australian activewear brands tend to favour.

The Upside to UK Size Conversion

The Upside SizeUK Size (approx.)Bust (cm)Waist (cm)Hips (cm)XXS4 – 678 – 8260 – 6484 – 88XS6 – 882 – 8664 – 6888 – 92S8 – 1086 – 9068 – 7292 – 96M10 – 1290 – 9472 – 7696 – 100L12 – 1494 – 9876 – 80100 – 104XL14 – 1698 – 10280 – 84104 – 108

These measurements are a general guide. Always cross-reference with the specific product page on The Upside's site, as their extended and newer collections can vary slightly, particularly across their ribbed and woven ranges.

How the Fit Varies by Garment

The Upside makes a wide range of pieces — from sculpting leggings to woven run shorts, oversized hoodies to structured tennis dresses — and they don't all behave the same way. Here's the honest breakdown:

Leggings & Bike Shorts: True to size for most, but if you have fuller hips or thighs, go up one. Their signature ribbed styles in particular have a firm compression fit — brilliant once on, but less forgiving if you're mid-size. The high-waist styles are genuinely stomach-smoothing, which is half the reason people pay the price they do.
Sports Bras: Size up. Consistently. The Upside sports bras run small in the cup and the band — I've heard this from virtually everyone who wears them. Go up one size from your usual and you'll be comfortable. Stick with your usual and you may find yourself having a quiet emergency mid-downward dog.
Tops & Tanks: True to size for a fitted look. If you prefer a relaxed, off-duty feel — which many of their tops lend themselves to beautifully — go up one for that effortless, draped-over-the-legging look that's all over their Instagram.
Hoodies & Sweatshirts: These are designed with a relaxed, oversized silhouette, so true to size gives you that intentional volume. Only go up if you're specifically looking for a very generous, cocooning fit.
Shorts: True to size in the woven and terry styles. The waistbands are adjustable on many styles, which is a useful touch. Fit tends to be more generous through the seat than the leggings, so some people actually find these run slightly large.
Dresses & Playsuits: Size up one. Their activewear dresses are cut for performance and fit close to the body. Given the price point, I'd always recommend checking the length measurements too — some styles sit quite high on the thigh, which is personal preference territory.

Ella's Styling Tips for The Upside

Once you've cracked the sizing, The Upside is one of those brands where the pieces really do the heavy lifting for you. A few things I always suggest:

Lean into their tonal dressing — wearing the matching set in one of their signature colour stories (the sage greens, the warm terracottas, the classic blacks) looks quietly expensive and requires zero effort
Their printed pieces are bold — if you're new to the brand, start with a neutral base legging and add one print piece. It's a much wearable entry point than going head-to-toe print
The hoodies and zip-ups work brilliantly styled over slip dresses or with wide-leg jeans for off-duty dressing — they're not just for the gym, and the brand knows it
Invest in the quality fabric ranges first — the Peached and Ribbed collections in particular are the ones customers rave about most consistently

High Street Activewear Alternatives Worth Knowing

The Upside sits at a premium price point — pieces regularly run from £80 to £200-plus — and while I genuinely think the quality justifies it, there are excellent alternatives at lower price points. Here are my picks, chosen specifically for their activewear credentials:

Sweaty Betty — The closest UK equivalent in terms of that fashion-meets-function approach. Their Power Leggings have a devoted following, their sizing is reliable, and they have a brilliant range of flattering styles. A go-to for women who want elevated activewear without the Australian import price tag.
Lululemon — Yes, they're everywhere, but for very good reason. Their Align leggings remain benchmark-setting in terms of feel, and their sizing is consistent and well-documented. If you've got Lululemon as your reference size, you'll find The Upside a similar fit.
Gymshark — Exceptional value at the mid-market level. Their Adapt and Vital collections in particular have impressed style editors and customers alike — genuine quality at a fraction of The Upside's price. Sizing runs slightly small so go up one.
Calvin Klein — Their Performance range is consistently brilliant — clean lines, excellent fabric quality, and a grown-up aesthetic that feels far more elevated than the price suggests. The bralettes in particular are a genuine find.
Abercrombie & Fitch — Don't overlook their activewear. Their YPB (Your Personal Best) range has been quietly building a strong reputation — great compression, on-trend colourways, and very competitive pricing. Sizing runs true to UK.
The White Company — For the softer end of activewear and luxe loungewear that bridges gym and home, The White Company's range is beautiful. Not performance-level, but for yoga, walking, and everyday wear, it's a genuinely lovely option.
Anthropologie — Their activewear edit pulls in some excellent independent and premium brands alongside their own label pieces. Worth checking for discovering new names and for beautifully curated prints that feel distinct from the usual activewear market.

Two Independent Picks You Should Know About

Varley — A London-founded premium activewear brand that deserves far more recognition than it gets in the mainstream. Think The Upside's aesthetic sensibility but with a distinctly British edge — clean, considered, and beautifully made. Their leggings are exceptional and their sizing runs true to UK. A genuine alternative if you love The Upside's ethos but want something a little closer to home.
PE Nation — Another Australian brand (yes, they really are doing something right down there) with a bold, graphic, colour-forward aesthetic. PE Nation sits at a similar premium price point to The Upside but with a more streetwear-influenced edge — think cropped hoodies, oversized logo pieces, and colour-block sets. Sizing runs true to size with a relaxed fit on their non-compression pieces.

📖 More from the Tellar Fashion Hub:

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