What Is Sizing Like at Rails?

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

Rails runs small — it's an American brand using US sizing, which typically means UK shoppers need to go up one to two sizes from their usual. If you're a UK 12 and you order a Medium thinking that's your size, there's a very good chance you'll end up in a frustrating wrestling match with the buttons. Go up. Every single time.

I fell down the Rails rabbit hole a few years back when a client of mine came back from a trip to Los Angeles absolutely obsessed with their plaid shirts. She'd bought three in her UK size and none of them fitted properly — too tight across the back, pulling at the chest. We exchanged them for a size up and suddenly they looked exactly as they should: that easy, slightly oversized, California-cool drape that makes a Rails shirt one of the most effortlessly stylish things you can own. The lesson stuck with me, and I've been telling clients to size up ever since.

Rails is a Los Angeles brand that launched in 2008 and has built a devoted following — particularly in the UK — for their signature plaid shirts, silk blends, and luxuriously soft jersey pieces. The aesthetic is relaxed but considered: think Californian off-duty dressing done with genuinely lovely fabrics. Their pieces are designed to be worn loose and easy, but the actual garment measurements are cut to US proportions, which run narrower through the shoulders and body than UK sizing. Factor that in and you'll be absolutely fine.

Rails Women's Size Conversion Guide

Rails uses US sizing with XS through XL labels across most of their range, plus some numerical sizing (0–12 US) on specific styles. Here's how it maps to UK sizes — and remember, when in doubt, go up:

Rails SizeUS SizeUK SizeEU SizeBust (cm)Waist (cm)Hip (cm)XS0–26–834–3681–8462–6587–90S4–68–1036–3885–8866–6991–94M8–10124089–9470–7595–100L10–12144295–10076–81101–106XL1416–1844–46101–10882–89107–114

💡 Ella's tip: Rails intentionally designs many of their shirts and tops to be worn with volume — slightly oversized through the body, slightly dropped at the shoulder. Don't fight this. Sizing up gives you that signature Rails drape rather than a too-tight fit that kills the whole vibe. If you're between sizes, always go to the larger one.

Sizing by Garment — The Honest Breakdown

Rails has expanded well beyond the shirt that made them famous — they do dresses, knitwear, trousers, and jackets now too. Here's how sizing plays out across the range:

Plaid & Check Shirts: The piece that built the brand and still their strongest offering. These are designed with a relaxed, slightly boxy silhouette — broader through the shoulder, easy through the body. Size up one from your usual UK size as a default. If you have broad shoulders or a larger bust, go up two. The shirts are meant to be untucked or half-tucked, so a little extra length and volume is entirely intentional and looks brilliant.
Silk-Blend Blouses & Tops: Rails does some genuinely gorgeous silk and viscose-blend blouses — the kind that look expensive, wash beautifully, and earn you compliments every single time you wear them. These tend to run a touch more true to size than the shirts because they're cut with slightly more drape and less structure. Still, if you're between sizes, go up. Silk and silk-blends are unforgiving when too tight and beautiful when they have room to move.
Dresses: Rails' dresses have become increasingly popular and for good reason — the fabric quality is exceptional. Their shirt dresses and midi styles follow the same logic as their shirts: size up one. Their more slip-style and fluid dresses in viscose blends can be slightly more generous, but I'd still lean towards going up rather than down.
Knitwear: Their knitwear range has grown significantly and is really lovely — soft, well-textured, and with that same considered-but-casual aesthetic. Knitwear at Rails runs similarly small to their shirts, so the same rule applies: size up one. Their oversized styles are genuinely oversized, so if a style is labelled as oversized, you may find your usual size (already sized up once) works perfectly.
Trousers & Shorts: Rails' bottoms follow US numerical sizing on some styles, which can be confusing. A US 6 is roughly a UK 10; a US 8 is roughly a UK 12. Their trousers tend to cut slim through the thigh and hip compared to UK sizing, so if you're carrying any volume through the hip or thigh, go up at least one size. Waistband fits on their trousers can be fairly snug — always check the hip measurement against the garment measurements, not just the size label.
Jackets & Outerwear: Rails has a small but really strong outerwear offering — their quilted and sherpa styles in particular. These are cut for layering over light pieces, so if you want to wear a chunky knit underneath, factor that in and go up two sizes rather than one. Their leather-look and tailored jacket styles run slimmer, so stick to one size up.

My Fit Tips for Getting Rails Right

Rails is one of those brands where once you've cracked the sizing, you become a complete convert. Here's what I tell every client before they order:

The shoulder seam is your guide. On any Rails shirt or jacket, the shoulder seam should sit right at your natural shoulder point or very slightly dropped — their aesthetic is built around that slightly relaxed shoulder. If it's sitting mid-way down your upper arm, you've gone too big. If it's pulling inward, you need to go up.
Don't order based on the label alone. Rails' product pages on their website and at Selfridges, MATCHESFASHION, and other UK stockists usually include garment measurements (not just body measurements). Measure the actual chest, shoulder, and body length on a shirt you already own and love, then compare it to the Rails garment measurements. That's far more reliable than any size chart.
Fabric content changes everything. A Rails shirt in 100% cotton sits differently to one in their cotton-modal blend or viscose. The blended fabrics have more drape and are more forgiving. Pure cotton will feel stiffer initially and has less stretch — give it a size up if you're on the edge.
Rails is worth buying in person if you can. They're stocked at Selfridges, Harvey Nichols, and a handful of independent boutiques across the UK. The difference between a Rails shirt that fits and one that doesn't is significant — it's worth trying a few styles to understand your Rails size before ordering online.
Returns are generally straightforward. If you do order online and it doesn't fit, most major UK stockists (ASOS, Selfridges, Net-a-Porter) have solid return policies. Order two sizes and keep the one that fits — it's genuinely the easiest approach with an American brand you're new to.

Love the Rails Aesthetic? Here Are Smart Alternatives

Rails sits in a sweet spot — better fabric quality than the high street, more accessible than full luxury, with a very specific Californian-cool identity. If you love the look, here's where else I'd shop:

High Street & Mid-Market Picks

Anthropologie — Consistently the best high street option for the Rails customer. Their shirts and blouses have a similar relaxed, slightly boho quality and are often made in comparable fabric weights. The sizing is also US-influenced, so the same size-up rule applies.
The Gap — An underrated pick for anyone who loves a classic plaid shirt done well. Gap's flannel and cotton shirt offering is genuinely excellent quality for the price, and their US-to-UK sizing conversion is consistent and predictable.
Abercrombie & Fitch — Another American brand that's transformed its offering in recent years. Their shirts and knitwear now have a surprisingly premium feel, and for the Rails customer who wants that west coast casual aesthetic without the price tag, Abercrombie is well worth a look.
All Saints — For the darker, more utilitarian take on the Rails shirt — think charcoal, washed black, deep navy rather than classic plaid — All Saints delivers brilliantly. Their shirt quality is strong and the aesthetic is distinctly cool rather than preppy.
Hush — A brilliant British option for women who love Rails' effortless, relaxed sensibility but want UK sizing and UK customer service. Their shirts, blouses, and knitwear are quietly excellent and the sizing is far more forgiving for UK-shaped bodies.
Whistles — For the more grown-up, polished take on the relaxed shirt and blouse aesthetic. Whistles does a consistently strong range of silk and printed blouses that appeal directly to the Rails customer who wants slightly more edge and refinement.
Cos — If you love Rails' cleaner, more minimal silk and viscose styles rather than the plaid shirts, COS is the obvious alternative. Beautifully considered fabrics, great drape, and a similarly understated approach to dressing.

Premium Picks

Vince — Another LA-born label with a very similar DNA to Rails — luxe basics, incredible fabric quality, relaxed but considered. Slightly more expensive, but if you've fallen for the Rails aesthetic, Vince is where you naturally end up next.
Equipment — The silk shirt brand that arguably started the whole "luxury casual shirt" conversation before Rails came along. Their signature silk shirts are the benchmark the whole category is measured against. Worth every penny for a wardrobe investment piece.

Independent & Left-Field Picks

Trovata — A small California-based brand that never quite got the mainstream attention it deserved. Deeply similar aesthetic to Rails — relaxed tailoring, lovely textiles, that west coast ease — but with a more individual, less ubiquitous feel. Worth seeking out if you want the Rails vibe without wearing what everyone else is wearing.
Wyse London — A brilliant British independent label with a seriously devoted following among women who appreciate good fabric and considered, personality-led design. Their knitwear and blouses are exceptional, and unlike Rails, they're sized for actual UK women. I recommend them constantly and they never disappoint.

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