Should I Size Up for Outerwear, Coats & Jackets? A Complete Fit & Sizing Guide

When buying a coat or jacket, especially online, the question that stumps many shoppers is: Should I size up? The answer isn’t always straightforward. It depends on garment construction, your intended layering, shoulder width, body shape, and how the brand cuts its outerwear. This guide breaks it all down.

Why Outerwear Sizing Feels So Tricky

Unlike T-shirts or jeans, outerwear isn’t worn close to the body—it’s designed to be the outermost layer, sometimes layered over knits or suits. That alone creates complications in sizing.

Key differences in outerwear sizing:

More structure: Tailored coats and padded jackets often have set seams, shoulder pads, or defined silhouettes.
Limited stretch: Unlike jersey fabrics, outerwear materials like wool, nylon, or technical blends don’t allow much give.
Layering expectation: Most coats are designed assuming you’ll wear something underneath. But how much layering is expected? That varies by brand and country.

When You Should Size Up

1. You plan to layer heavily

If you live somewhere cold or wear thick jumpers and hoodies often, sizing up gives you that needed breathing room. Try raising and crossing your arms in the mirror—if there’s tightness at the upper back or underarms, you need more ease.

2. You have broad shoulders or a larger bust

Structured coats often don’t accommodate strong shoulders or fuller busts. Sizing up ensures the jacket lies flat, doesn’t pull at the chest, and doesn’t restrict shoulder movement.

3. You’re buying double-breasted styles or sharp tailoring

Many double-breasted coats run narrow to maintain a sleek fit when buttoned. If you’re between sizes or prefer a looser look, size up.

4. The coat is European sizing or unisex

Many European or Korean brands run small compared to UK or US sizing. Unisex fits also often assume male proportions, which may not work for curvier frames.

When You Shouldn’t Size Up

1. Oversized is the intended cut

If the coat already has a deliberately oversized cut (e.g., cocoon or boyfriend styles), sizing up might drown your frame. Always check product descriptions for phrases like "relaxed fit", "oversized", or "generous cut".

2. You’re petite

For shorter frames, sizing up can overwhelm proportions and make a coat look boxy or frumpy. Instead, opt for petite-fit outerwear, tailored to shorter torsos and sleeve lengths.

3. It’s a light jacket or trench

Transitional jackets and raincoats are meant to be worn over a single layer, not chunky knits. Sizing up here can cause gaping at the collar or uneven draping.

The Technical Rule: "Shoulder Fit First"

The golden rule for outerwear? Fit the shoulders first. The shoulder seam should sit just at the edge of your natural shoulder. If it pulls inward, it’s too small. If it drops more than an inch down your arm, it’s too big.

Getting the shoulders right ensures the rest of the coat falls properly. It’s extremely difficult and expensive to alter shoulder seams, whereas waist and sleeve adjustments are far easier for tailors.

International Sizing Confusion

Sizing inconsistencies are rampant across brands—and outerwear is no exception.

A UK 10 might be a tight Medium at COS but a loose Small at Uniqlo.
Zara coats often run smaller than their labelled UK size.
Mango and Massimo Dutti coats fit narrow in the shoulders and upper arms.
American brands like Everlane or J.Crew tend to size more generously.

These inconsistencies make it difficult to rely on traditional size charts alone. Many customers resort to trial and error—but there’s a better way.

How to Choose the Right Outerwear Size Without Guesswork

1. Measure Your Bust, Waist and Hips

Even for coats, your bust and shoulder width are the most crucial indicators. Measuring across the fullest part of your bust while wearing layers gives you a clearer sense of how a coat will fit.

2. Account for Layering

Add 2–4 cm (or about 1–1.5 inches) of "ease" for your bust and waist to accommodate sweaters or blazers beneath. Brands that don’t build in ease may require you to size up.

3. Use a Tool That Does It for You—Enter Tellar.co.uk

How Tellar.co.uk Solves Outerwear Sizing

Tellar.co.uk is the UK’s leading sizing tool—specifically designed to remove all sizing guesswork, especially for tricky garments like coats and jackets.

Instead of checking 10 different size charts, Tellar does the work for you. Here's how it works:

🔍 Enter your bust, waist and hip measurements or your known size in a favourite brand.
🧥 Tellar instantly matches your body to the sizing charts of over 1,500 brands, including COS, Reiss, Arket, Massimo Dutti, Everlane, & Other Stories, and more.
📏 See your perfect size in every brand in real-time—no guesswork, no errors.
📉 Avoid returns due to bad sizing.
🎯 Get personalised sizing based on your largest measurement, ensuring coats always fit your shoulders, bust or hips properly.

Always Free, Always Honest

No downloads, no sign-ups needed—Tellar.co.uk works right in your browser. And it’s not just a tool…

Explore the Free Fashion Library

The Tellar Fashion Hub includes thousands of expert-written guides covering:

Style advice by body shape
Flattering outerwear styles for petites, plus size, tall
Brand comparisons, shopping tips, and more

All content is:

✅ Honest
✅ Independent
✅ Always free

Create your free profile here:

➡️ https://www.tellar.co.uk/create-profile/

Use the Store Lookup Tool:

➡️ https://www.tellar.co.uk/store-size-lookup/

Download a free measuring tape:

➡️ https://www.tellar.co.uk/printable-measuring-tape/

Additional Resources

Follow Tellar.co.uk for More Sizing & Style Advice

Instagram: @Tellarsizing
Twitter/X: @TellarSizing
Facebook: Tellar Sizing
Pinterest: TellarSizing

Final Word

Sizing up for outerwear isn’t always necessary—but it can make or break your fit depending on your shape, layering habits, and the brand’s tailoring. The smarter solution? Let Tellar.co.uk calculate it for you—your body, matched to the exact right size across 1,500+ brands, instantly.

Find your size in 1,500+ brands real-time. It’s free & easy.