Should I Size Up or Down in Clothing? (UK & USA Guide)

If you’ve ever stood in a fitting room wondering whether to try the next size up or down, you’re not alone. Sizing inconsistencies plague both high street and designer brands across the UK and USA. In fact, it’s now common to be a size 10 in one shop and a 14 in another—even when trying the same type of garment.

This guide will help you:

Understand the difference between UK and US sizing
Know when to size up or down based on fabric, brand, or fit
Shop smarter with high street and luxury labels
And finally, how Tellar.co.uk solves this dilemma completely—with accurate, brand-matched sizing for your body.

🧵 Why Clothing Sizes Vary

1. No global sizing standard

While there are general guidelines for UK (6–24) and US (0–18) sizing, brands interpret these differently. One UK 12 might have a 29” waist, another a 31”.

2. Brand fit philosophy

Luxury brands like Reiss or The Row may run narrow for a tailored aesthetic. US brands like J.Crew or Everlane may add ease for comfort and layering.

3. Fabric and cut influence size

Stretch fabrics (jersey, elastane blends): Often allow you to size down.
Structured fabrics (denim, wool, taffeta): May require sizing up for movement.
Oversized garments: Already designed to be roomy—don’t size up.
Tailored items: Should fit more closely; if it pulls or pinches, size up.

📖 Related:

The Ultimate Clothing Sizing Guide

Finding Your Clothes Size: The Ultimate Guide

UK vs USA vs European Clothing Sizes: The Ultimate Guide

🔄 When Should You Size Up?

Fitted dresses or trousers in rigid fabrics (e.g. Zara or COS): Size up to avoid tightness across the hips or bust.
Luxury brands with European tailoring (e.g. Max Mara, Sandro): Often cut smaller—size up for shoulder and chest comfort.
Wool coats and suiting: Size up if layering is expected underneath.
Brands that run small: Massimo Dutti, Club Monaco, & Other Stories often receive this feedback.

📖 Related post:

What Size Am I in Next?

🔽 When Should You Size Down?

Stretch denim or jersey dresses: These expand with wear—go smaller for a sleeker silhouette.
Oversized trends (e.g. COS wide trousers, Arket shirts): Often cut extremely loose; a smaller size gives more control.
US brands known to run large: Banana Republic, J.Crew, Old Navy—UK buyers often find they can size down.
Relaxed-fit knits or coats: Choose a smaller size to avoid swamping your frame.

🛍 High Street vs. Designer: How Sizing Behaves

Brand	Tends to run	Sourcing country
Zara	Small	Spain (EU fit)
COS	True to size/slightly large	Sweden
H&M	True to size	Sweden
& Other Stories	Slightly small	France/Sweden
Massimo Dutti	Small	Spain
Arket	Oversized cuts	Sweden
Reiss	Narrow/tailored	UK
J.Crew (USA)	Large	USA
Everlane (USA)	Slightly large	USA
The Row	Tailored, TTS	USA/Luxury
Max Mara	Small across bust/shoulders	Italy

🧠 Smart Fit Rules to Follow

If it pulls, size up: Buttons gaping? Waistband digging? Size up and tailor if needed.
If it stretches out, size down: Stretch denim, jersey dresses, knit trousers tend to grow.
Always size for the largest part of your body: Then tailor other areas. E.g., if you have broad shoulders, size up for tops and adjust the waist.
Avoid panic-sizing: Labels are not standardised; your size does not define your body.

🎯 The Sizing Solution: Tellar.co.uk

No matter how experienced you are, guessing between sizes wastes time and money. Tellar.co.uk removes the guesswork—matching your exact body shape to real-world brand sizing in over 1,500 UK and USA brands.

✅ How Tellar.co.uk Works

Measure once using bust, waist and hip—or input a brand size you already wearInstruction on Posts
Use the Store Size Lookup Tool to get your precise size in COS, Reiss, Arket, Everlane and moreInstruction on Posts
Shop with confidence—no more duplicate orders or returnsInstruction on Posts
Always free—works instantly in-browser. No apps. No login feesInstruction on Posts

👉 Try it now:

🧵 Tellar’s Fashion Hub: Free, Unbiased, Independent

Beyond sizing, Tellar’s Fashion Hub is a deep library of free, stylist-written posts. Explore thousands of articles on:

Sizing breakdowns
Fit science
Brand comparisons
Capsule wardrobe advice
Body shape styling

📚 Explore key posts:

📲 Follow Tellar for Live Styling Advice & Fit Science

Stay connected with fit science updates, brand reviews, and daily wardrobe tips:

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

Final Thought

Whether you need to size up or down depends on cut, brand, and body proportions—but your best tool is knowing your body measurements and matching them to the specific brand you’re shopping. Tellar.co.uk does that in seconds.

It’s free. It’s accurate. It saves time, money, and stress.

Ready to shop smarter? Visit www.tellar.co.uk today.

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