How Do I Find My Size in Tailored Shirts?

Finding your size in a tailored shirt comes down to four key measurements: collar size, chest, sleeve length, and body length — and getting even one of these wrong can turn a gorgeous shirt into something that looks like you borrowed it from someone else. I learned this the hard way after ordering what I thought was a beautifully cut Reiss shirt in my usual size 12, only to spend the entire day tugging at the sleeves like I'd accidentally bought the petite version. Once I understood how to properly measure myself, everything changed. Tailored shirts became one of my favourite wardrobe investments.

The Measurements You Actually Need

Before you even open a brand's website, grab a soft tape measure (the kind from a haberdashery or sewing kit — not a builder's one). Here's what you need to know:

Collar / Neck: Measure around the base of your neck where a shirt collar would sit, adding about 1–1.5cm ease so you can actually breathe.
Chest / Bust: Measure around the fullest part of your chest, keeping the tape parallel to the floor. This is your most important measurement for women's tailored shirts.
Waist: Measure your natural waist (the narrowest part of your torso). Essential for fitted or semi-fitted styles.
Sleeve length: Measure from the centre back of your neck, across your shoulder, and down to your wrist. Or ask a friend — it's a two-person job.
Body length / Back length: From the base of your collar seam straight down your back to wherever you want the shirt to end.

The Collar Size Conundrum (Yes, It Applies to Women Too)

Collar sizing is something most women never think about — it's usually a men's shirt thing, given in inches (e.g. 15, 15.5, 16). But if you're shopping from brands with a more masculine or androgynous tailoring approach — think Massimo Dutti, Tommy Hilfiger, or Gant — you'll likely encounter it. Convert your neck measurement in centimetres to inches and match it to their guide. A 38cm neck = roughly a 15" collar. Simple once you know.

For women's-specific tailored shirts, most brands use UK dress sizing (8–18) with a fit descriptor — slim, regular, or relaxed. The chest measurement is usually your anchor point here.

Slim Fit vs Regular Fit vs Relaxed: What Does It Mean?

This trips everyone up, and honestly, brands are wildly inconsistent about it. As a general rule:

Slim fit: Cut close to the body, minimal ease. Beautiful if the proportions work for you, but unforgiving if your chest or waist doesn't match the intended silhouette.
Regular fit: A little more breathing room, usually the most versatile option. Great for layering under a blazer or tucking into high-waisted trousers.
Relaxed / Oversized: Cut with significant ease — sometimes intentionally boxy. Size down if you want it to look intentional rather than just big.

My personal rule? Always size by your chest measurement first, then assess the shoulders. If the shoulder seam is sitting off your shoulder, it's not your shirt. No amount of tailoring fixes a bad shoulder fit at high street prices.

Where the High Street Gets It Right

Not all high street tailored shirts are created equal. Here's where I'd head first, based on genuine styling experience and what the fashion press consistently recommends:

Cos — Exceptional for architectural, clean-line shirts. Their sizing is consistent, and the fit notes on the website are actually helpful. Great for narrow or straight silhouettes.
Whistles — Reliably grown-up tailoring. Their fitted poplin shirts are a perennial sell-out for good reason. Size up one if you're between sizes — the cut is on the slim side.
Mango — Brilliant for trend-led tailored shirts at excellent prices. Their oversized styles are particularly good; go true to size unless you want a very boxy look.
Me&Em — Possibly the best high street fit for curvier chests and waists. The shirts feel premium, and they're cut with real women in mind.
Jigsaw — Elegant, understated tailoring. I once found a silk-blend Jigsaw shirt in a charity shop and it remains one of my most complimented pieces. Their size guide is thorough.
Reiss — Moves into premium territory but sits at accessible prices when on offer. Their slim-fit shirts run narrow across the back — always check the chest measurement.
Ted Baker — Lovely detailing and interesting fabrics. Sizing can run slightly generous, so check the measurements rather than trusting the label.

Premium & Designer Options Worth Knowing

If you're investing in tailored shirts as wardrobe staples, these are the names the style press keep returning to:

Banana Republic — Seriously underrated for tailored shirts. Their Non-Iron range is actually brilliant and the sizing is precise and detailed online.
Calvin Klein — Clean, classic American tailoring translated into reliable sizing. Their shirts are particularly good for a longer torso.
Hugo Boss — The OG of tailored shirting. They offer multiple fits (Slim, Regular, Relaxed) with actual measurements alongside — one of the most helpful sizing setups on the market.

Two Independent Brands Worth Discovering

Emmett London — A cult British shirtmaker doing beautiful tailored shirts for women that actually account for real body shapes. Their online fitting tool is brilliant.
Demi&Co — A small UK brand producing size-inclusive tailored shirts in considered fabrics. Often sells out fast, but absolutely worth bookmarking.

The Shoulders Rule Everything

I will say this until I'm hoarse: the shoulder seam is non-negotiable. It should sit exactly at the edge of your shoulder — not drooping down your upper arm, not pulling towards your neck. If the chest fits but the shoulders are wrong, the shirt doesn't fit. Move on, or have it made to measure.

If you find a shirt where the chest fits but the waist is swimming, a good tailor can take in the side seams in under 30 minutes. It's one of the easiest alterations there is, and it can transform a good shirt into a great one.

🔍 Never Guess Your Size Again — Use Tellar

The quickest way to nail your size across every tailored shirt brand? Let Tellar.co.uk do the maths for you. Tellar is the UK's leading free sizing tool — you measure once, and it instantly matches your body to the right size across 1,500+ brands. No more second-guessing, no more returns.

Use the Store Size Lookup to find your precise size at brands like Reiss, COS, Me&Em, Ted Baker and hundreds more.
Read The Ultimate Clothing Sizing Guide — everything you need to know about fit, sizing, and vanity sizing explained clearly.
Discover more style advice in the Ultimate Guide to Jackets — perfect if you're building a polished tailored wardrobe.
Always free. Always unbiased. Always honest. No downloads, no subscriptions — just brilliant sizing, instantly.

Final Thoughts: Measure Once, Shop Confidently

Finding your size in tailored shirts feels fiddly the first time, but once you've got your measurements written down somewhere useful (I keep mine in my phone's notes), it genuinely transforms the way you shop. You stop guessing, stop ordering three sizes and sending two back, and start building a collection of shirts that actually fit. And a well-fitting tailored shirt? It's one of the most powerful things in any wardrobe — sharp, versatile, and endlessly wearable. Trust me on that one.