What is sizing like at Rat & Boa?

By Ella Blake – Senior fashion stylist & Founder | Tellar — Always honest, unbiased, & unsponsored post

Rat & Boa sizing runs small and, frankly, all over the place depending on the style — the signature bias-cut satin maxis tend to come up snug through the bust, while the stretchier mesh and bodycon pieces are far more forgiving. So the honest answer is there is no single "Rat & Boa size." You can be a clean small in one dress and squeezing into a medium in the next, and that catches a lot of people out.

I learned this the hard way. I ordered the brand's most-hyped slip dress in my usual size for a friend's vineyard wedding, felt very smug about it, and then couldn't get the zip past my ribcage. Mortifying. Two days before the event I was frantically reordering a size up via next-day delivery. The bigger one was perfect — but I'd have saved myself the panic if I'd understood how this brand actually fits before I clicked buy.

So, does Rat & Boa come up small?

Generally, yes — but with caveats. Here's how it breaks down across their range:

Bias-cut satin maxis (their bread and butter): run small in the bust and across the back. If you're an hourglass or fuller on top, size up. The cut clings on the diagonal, so there's very little give.
Slip and cami styles: truest to size if you're narrow through the hip. Curvier hips? Take your usual size and accept a closer fit, or size up for comfort.
Mesh, lace and stretch pieces: the most forgiving. Take your normal size, or even size down if you want that proper second-skin, bodycon look.
Straps: the good news — most of the bias maxis have adjustable straps, so length is rarely the problem. It's almost always the bust and back you need to watch.

The fabric is a big part of why fit feels unpredictable. Rat & Boa lean on silk and viscose blends that drape beautifully but have almost no stretch, so the dress sits exactly where the pattern intends — there's nowhere to hide and nothing to "give." It's what makes them look so expensive in photos, and so unforgiving if you've guessed wrong.

A quick, honest word on quality and returns

The make is genuinely lovely — lined bodices, neat elasticated cuffs, that liquid satin drape. But two things to know before you commit: the sizing is inconsistent between styles (reviewers routinely report a perfect small in one dress and a tight one in another from the same order), and the returns window is short. Order early, not the week of your event, and check the current returns policy before you buy two sizes "just in case."

How I'd actually style it

These are dresses that want to be the whole outfit. My rule: let the dress do the talking and keep everything else quiet. A bias satin maxi needs nothing more than a sleek heel, a tiny bag and your hair off your face. Because the backs are often open and the necklines plunge, a stick-on bra or going bra-free is usually the move — structured underwear ruins the line. For colder months, throw a sharp tailored blazer or a longline wool coat over the top and let the slip peek out beneath. That contrast of slouchy-glam dress and crisp tailoring is endlessly chic.

Where else to shop if Rat & Boa isn't your fit

If the sizing gamble puts you off, or you want the look at a different price point, here's where I'd send a client for that same slinky, occasion-ready energy.

High street

Reiss — the closest high-street match for elevated slip and column dresses; fit is consistent and grown-up, ideal if you found Rat & Boa too unpredictable.
Whistles — masters of the understated bias-cut and clean satin midi; their fit tends to be true and forgiving through the bust.
Mango — brilliant for affordable satin slips and going-out dresses that photograph well above their price.
Coast — a proper occasion specialist; go here for structured event dresses if a flimsy bias cut feels too exposing.
Warehouse — reliably good satin and ruched party styles with a bit more give in the fabric.
Zara — for the trend-led, of-the-moment going-out dress; sizing varies, so it's a try-before-you-trust shop.
Oasis — pretty, occasion-led dresses that often run a touch more generously than Rat & Boa.

Premium

Reformation — the obvious step up: bias-cut slip dresses with the same Instagram-girl appeal and a more dependable size chart.
Ghost — long-standing experts in bias-cut satin and viscose; if you love the Rat & Boa drape but want a kinder fit, start here.

Luxury / designer

Galvan London — the gold standard for liquid satin column dresses; investment pieces that fit like couture.
Saloni — print-led, romantic occasion dresses with the same drama Rat & Boa trades on, cut beautifully.

Two off-the-radar names worth knowing

Faithfull the Brand — a Bali-based independent label doing dreamy slip and bias dresses in gorgeous prints; a lovely under-the-radar alternative with a softer, more relaxed fit.
Sau Lee — an independent occasionwear label specialising in flattering, structured event dresses; perfect if you want the wow-factor without the bias-cut sizing roulette.

Never gamble on Rat & Boa sizing again

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