What is Sizing Like at Fashion Union?

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

Fashion Union runs slightly small compared to standard UK sizing, so if you're between sizes, I'd always suggest sizing up — a tip that applies across a lot of their trend-led pieces, particularly the bodycon styles and structured tailoring they're known for.

I'll be upfront: Fashion Union isn't a brand that always makes it onto my radar as a stylist, but when a client comes to me asking about it, I take it seriously. It sits firmly in the affordable, fashion-forward space — and I've helped plenty of women navigate the sizing there, mostly because a poorly fitting dress from Fashion Union can look very different from the product shots. Get the fit right, though, and there are some genuinely lovely pieces.

The General Sizing Verdict

Fashion Union's sizing broadly follows UK standard conventions (sizes 6 through 18), but in practice, their cuts can feel tighter through the bust and hips than you'd expect. This is especially true on their bodycon dresses, co-ords, and anything cut close to the body. Their more relaxed silhouettes — oversized knits, floaty midi skirts — tend to be more forgiving.

Bust: Can run small, especially on fitted styles. If you're fuller busted, size up.
Waist & hips: Generally consistent, but bodycon cuts are tight — go a size up if in doubt.
Length: Mini and midi styles are cut for an average UK height of around 5'4"–5'6". If you're taller, minis will be very short and midis may hit at an awkward spot on the calf.
Petite shoppers: Fashion Union doesn't have a dedicated petite range, so hemlines and sleeve lengths can overwhelm shorter frames.

My Honest Stylist Take

I once helped a client pick a bodycon satin slip dress from Fashion Union for a birthday dinner. She'd ordered her usual size 10 — and the split was essentially on her hip before she'd even moved. We swapped to a 12 and it was stunning. The moral? Don't be precious about the label. Fashion Union is a fast fashion brand that sizes for trend, not always for anatomy.

That said, I've seen their blazers and wide-leg trousers work brilliantly on clients who know their measurements. The quality for the price point is decent — especially their occasion and going-out pieces which photograph really well and won't break the bank for a single night out.

Fabric Matters More Than You Think

A lot of Fashion Union's pieces are made from stretch-blend fabrics — and this can work in your favour. That slight elasticity in a bodycon dress means a size 10 might technically fit a 12 if you're okay with the fit being very form-fitting. However:

Stretch fabrics cling — which is the point, but not for everyone.
Non-stretch structured pieces (blazers, tailored trousers) will be more unforgiving — size up on these confidently.
Knitwear from Fashion Union tends to be quite generous — I'd say true to size or even slightly oversized.

Best Styling Tips for Fashion Union Pieces

Their co-ord sets are a strong suit — they're often designed to be worn together and the sizing on both pieces is matched accordingly, which makes life easier.
Pair their bodycon pieces with a blazer to balance proportions and add polish.
Midi skirts from Fashion Union work beautifully for evening — try styling with a tucked-in blouse and block heel.
If you're buying for a special occasion, always check the return policy and order two sizes to try at home.

High Street Alternatives — When Fashion Union Doesn't Fit

Sizing confidence is everything, and if you find Fashion Union's cuts aren't working for your shape, there are plenty of high street brands that serve the same aesthetic with better size consistency:

River Island — Great for party and occasion dressing with a very similar aesthetic to Fashion Union but generally more consistent sizing. Their going-out pieces are a proper go-to.
Topshop (now online via ASOS) — A natural Fashion Union alternative. The sizing runs truer and the range is huge for trend-led occasion pieces.
ASOS — Incredible for bodycon and occasion dresses with proper size filtering. Petite, tall, and curve options make this a far more inclusive choice.
Warehouse — Slightly more polished than Fashion Union, brilliant for tailored going-out pieces and midi dresses with a cleaner fit.
Oasis — Back online and worth a look for feminine, occasion-ready styles. Great for those who want Fashion Union's feel with a slightly more grown-up finish.
Coast — Perfect if you're looking for occasion wear that steps up in quality. Their dresses are beautifully cut and sizing is notably more reliable.
Phase Eight — If you want that dressy, event-ready look but with significantly better fabric quality and fit. Their midis are incredible and sizing is very consistent.
Anthropologie — Slightly higher price point, but for those wanting something more unique with better craftsmanship than Fashion Union's fast fashion offering.

Premium & Luxury Picks

If you love the aesthetic Fashion Union is going for but want to invest in pieces that'll last beyond a season:

Reiss — For beautifully cut occasion dresses and co-ords at a premium price point. The quality leap from Fashion Union is significant and the sizing is reliable and consistent.
Zimmermann — For the elevated, feminine occasion piece. Yes, it's designer money, but a Zimmermann mini or slip dress is something you'll wear for years, not just one Saturday night.

Two Independent Brands Worth Knowing

Every post I write, I want to shout out a couple of independent brands that deserve more attention — these aren't brands you'll find on every high street, but they're brilliant:

Kitri — A London-based independent label that does occasion and going-out dressing exceptionally well. Sizing is very true-to-UK and the quality is miles ahead of fast fashion. A brilliant step up if you love Fashion Union's aesthetic but want something more considered.
Fanfare Label — A sustainable UK independent focused on responsible fashion. Their occasion pieces are beautiful, sizing runs true, and you're buying into something that actually lasts. A lovely antidote to fast fashion overconsumption.

Never Guess Your Size Again — Tellar.co.uk

Sizing anxiety is real — and honestly, it's one of the most common things I deal with as a stylist. That's why I always point clients to Tellar.co.uk — the UK's leading free sizing tool that matches your exact measurements to 1,500+ brands instantly. No more guessing, no more returns pile shame.

📏 Measure once — bust, waist, hip, or use an existing brand size you trust.
🔍 Use the Store Size Lookup tool to get your precise size across hundreds of brands — COS, Reiss, Everlane, Arket, and hundreds more.
✅ Always free. No downloads. Works instantly in-browser.
📚 Plus — explore the Tellar Fashion Hub: a growing library of free, honest, unbiased style posts from our team of stylists. No sponsored content, no paywalls. Ever.

Honest sizing. Independent advice. Always free. That's Tellar. Visit tellar.co.uk →