Should I Size Up for Cashmere Jumpers?

By Ella Blake | Tellar Fashion Hub

Yes — in most cases, sizing up one size for cashmere is the right call. But how much depends entirely on the brand, the knit, and the look you're going for.

I've made this mistake so many times I've lost count. I'd find the most beautiful cashmere jumper — usually in a soft camel or heathered grey — order my usual size, and then spend the next week feeling vaguely strangled every time I put it on. Tight across the shoulders, pulling at the back, completely killing the luxurious drape that makes cashmere worth the investment in the first place. It took me an embarrassingly long time to accept that cashmere sizing is genuinely different from the rest of your wardrobe — and once I cracked it, everything changed.

Why Cashmere Fits Differently

Cashmere is a natural fibre, and unlike cotton or a rigid wool blend, it's designed to move with you. The best cashmere has a soft, fluid weight to it — it's supposed to skim, not cling. When you size down (or stick rigidly to your standard size), you lose that drape entirely. The fabric stretches across the bust, the shoulders look pinched, and the whole thing reads as budget knitwear rather than the considered piece it actually is.

There are a few other things going on too:

Cashmere relaxes with wear. A jumper that fits snugly in the shop will often feel tighter once you've worn it a few times and it's settled into shape.
Shoulder seams are everything. If the seam sits even slightly off your shoulder, the whole jumper looks wrong. Sizing up gives you a cleaner shoulder drop, which is actually more flattering on most body shapes.
Layering matters. Most of us wear cashmere over a base layer — a silk slip, a thin long-sleeve top. Your usual size won't account for that.
Brand sizing is wildly inconsistent. A size 12 in one brand's cashmere is a full size 10's worth of fabric in another's. This is where it gets genuinely maddening.

The Golden Rule (With Caveats)

My general rule is: size up one, especially for classic round-neck or crew-neck styles. For chunky, oversized, or fisherman knits, you might even want to go two sizes up to get that intentional slouch. For fitted turtlenecks or rib-knit cashmere, your true size usually works fine because the stretch is built in.

The silhouette you're after matters enormously. If you want that effortlessly thrown-on Parisian look — relaxed, slightly boxy, shoulder seam sitting mid-upper arm — size up. If you want clean and tailored, stick to your true size or even size down, but double-check the shoulder seam first.

What the Brands Actually Do

Not all cashmere is cut the same, and this is where I'd really encourage you to pay attention. Here's how I'd break it down across price points:

HIGH STREET

M&S — Their cashmere is genuinely brilliant value and consistently well-reviewed. It runs slightly generous, so check the measurements rather than defaulting to your size. Their Pure Cashmere range is a reliable go-to.
The White Company — Cuts slim. I cannot stress this enough — size up at least one, sometimes two. Their cashmere is beautiful but the fit is narrow across the back.
Jigsaw — Tends to run true to size or slightly slim; I always size up one here for anything that isn't a slim-rib style.
Hush — Great relaxed cashmere basics. Their sizing is fairly consistent and slightly relaxed, so your usual size works for fitted styles, but size up for anything listed as "relaxed" or "boxy" or you'll just end up with a very normal-fitting jumper instead of the slouchy one in the picture.
Boden — Solid mid-market option with honest sizing. Their cashmere runs true; I'd only size up if you're between sizes.
Cos — Their knitwear is cut oversized by design, so check the product notes carefully. I've ordered a size up here and ended up in something that could double as a blanket.
Whistles — A really underrated high street cashmere option. Cuts well for curvier figures; I'd still size up one for the shoulder fit.

PREMIUM

Me&Em — Excellent quality and proper sizing guidance on their site. Their cashmere runs slightly slim; I size up one and it's perfect every time.
Reiss — More tailored cuts; if you want a sleek, structured look, stick to size. For anything relaxed, go up.

LUXURY & INDEPENDENT

Brora — A Scottish cashmere institution. Their sizing is traditional and can run narrow; always check the chest measurement and size up if in doubt. Worth every penny.
Begg & Co — A stunning independent Scottish brand making exceptionally fine cashmere and merino knitwear. Their pieces are investment buys, sized generously and built to last decades. Less well known than the big names but absolutely exceptional quality.

How to Actually Check Before You Buy

The most reliable way to get your cashmere fit right — especially when shopping online — is to stop guessing based on label size and start checking the flat measurements. Most brands publish chest and length measurements in their size guides. Measure a jumper you already love, compare it, and buy accordingly. I promise this will save you so many returns.

Pay particular attention to:

Chest (measured flat, doubled): Should give you at least 2–4 inches of ease for a relaxed fit
Shoulder seam to seam: Should sit right at or just past your natural shoulder point
Sleeve length: Often overlooked — cashmere that's too short in the sleeve looks wrong instantly

Care After Sizing: Don't Ruin It

Once you've nailed the size, don't undo all that good work in the wash. Hand wash in cool water or use a wool/cashmere cycle, lay flat to dry (never hang — it will stretch and distort), and fold rather than hang in your wardrobe. And invest in a cashmere comb. Pilling is inevitable with real cashmere — it's a sign of quality, not a defect — but a good comb keeps it looking pristine.

Never Guess Your Size Again — Use Tellar

Getting cashmere sizing right is exactly why Tellar.co.uk exists. It's the UK's leading free sizing tool — matching your body measurements to over 1,500 brands instantly, so you stop second-guessing and start buying with confidence. No downloads, no subscriptions, no faff. Just your measurements and the right size, every time.

Simply measure once (bust, waist and hips, or use an existing brand size you trust), and Tellar tells you your precise size across thousands of brands — from M&S cashmere to Jigsaw knitwear to independent labels you might not have tried before.

👉 Use the Store Size Lookup tool here — works in-browser, always free.

And while you're there, dive into the Tellar Fashion Hub — a free library of honest, unsponsored style advice from our in-house stylists. No ads, no affiliate bias, no fluff. Just genuinely useful fashion guidance, including:

Sizing frustration is genuinely optional at this point. Tellar takes it off the table completely.