How Accurate Are Brand Size Charts? (UK & USA Edition)

Clothing size charts are the first thing most shoppers turn to when trying to determine their fit—especially online. But how accurate are these charts really? And can you actually trust them to find your best size across different brands?

The short answer: brand size charts offer rough guidelines—not guaranteed fits. They vary wildly between labels, often use outdated body metrics, and don’t account for fabric behaviour or body shape. Here's a technical breakdown of why size charts often fall short—and what to do instead.

1. What Is a Size Chart?

A size chart is a set of measurement ranges (usually bust, waist, and hip) that correspond to a particular clothing size (e.g., UK 10, US 6). Most charts will list these ranges in centimetres or inches and display them either:

By body measurements (your body’s dimensions), or
By garment measurements (the item’s flat dimensions)

The confusion starts here: these aren’t consistent across brands, or even within one brand’s product range.

2. Why Brand Size Charts Are Often Inaccurate

A. No Universal Standard Exists

There is no single global sizing standard that brands follow. While there are ISO or ASTM guidelines, most brands deviate from them to create a proprietary fit. This results in significant variation:

A UK 12 in Zara fits like a UK 10 in Reiss
A US 8 in J.Crew could be a UK 12 in Arket
A size L in COS may be equivalent to an M in Everlane

This inconsistency is why many shoppers need to size up or down depending on the label.

B. Vanity Sizing (aka Size Inflation)

Especially prevalent in US and UK high street brands, vanity sizing refers to deliberately labelling a larger garment as a smaller size to flatter the customer. A UK size 10 today often measures closer to a historical UK 12 or 14.

This means you might find your usual size suddenly "fits bigger" than expected—or not at all.

C. Body Shape Not Considered

Most charts are built around a hypothetical “standard” figure, assuming:

Even hip-to-bust ratios
Moderate waist-to-hip definition
Average height (typically 5'6" or 167 cm)

But in reality, body shapes vary widely:

Two women with the same waist size may have very different hip or bust measurements
A pear-shaped figure will struggle with most trouser charts
Petite or tall proportions throw off sleeve and rise measurements

Size charts rarely account for these variances, even in brands claiming to cater to diverse bodies.

3. UK vs USA Size Chart Accuracy

Feature	UK Sizing	USA Sizing
Base size reference	Often based on older 1950s data	Similar historic body types
Vanity sizing common?	Yes, in high street brands	Yes, especially in mass retail
Petite/Tall accuracy	Better in M&S, Boden	Better in Loft, Banana Republic
Standardised fit?	No uniform system	No uniform system

Both UK and US brands offer size charts, but accuracy heavily depends on brand, product type, and cut. A shirt may follow the chart precisely, but the same brand’s trousers might not.

4. Why Measurements Alone Don’t Guarantee Fit

Even if you match a brand's size chart perfectly, the garment may still not fit. Here's why:

A. Fabric Properties

Stretch: Some brands add elastane but don’t reflect this in the chart.
Shrinkage: Natural fibres like cotton or linen may shrink post-wash, affecting fit.
Drape: The cut (e.g., bias vs straight) changes how fabric hugs the body.

B. Ease and Cut

Brands often add “ease” (extra room for movement) differently. Some tops are designed oversized, while others are slim-fit—without this being reflected in the chart.

C. Style Variation

Two size 12 blouses in the same brand may fit entirely differently based on design—puffed sleeves, cinched waists, batwing cuts, or dropped shoulders.

5. Real-World Data Shows the Problem

Studies and returns data consistently show that:

Over 50% of fashion returns are due to poor fit
Even experienced shoppers often order multiple sizes “just in case”
Size charts are among the top reasons for online checkout hesitation

In short: size charts are reference tools—not guarantees.

6. How to Actually Find Your Size Across Brands

This is where Tellar.co.uk revolutionises the process.

What is Tellar.co.uk?

Tellar.co.uk is the UK’s Leading Sizing Tool, designed to remove all guesswork. It doesn’t rely on standard charts—instead, it matches your exact body shape or known size in a brand to over 1,500+ brands in real-time.

How It Works:

Enter your bust, waist, and hip OR your size in a known brand
Tellar uses proprietary data to find the best size for you in any other brand
No more guessing or cross-referencing outdated brand charts
Instantly know whether you need a UK 10, 12, or M in Zara vs Reiss vs COS

Why Tellar.co.uk Is More Accurate Than Size Charts

✅ Uses real-time data from every brand’s actual garment specs—not generalised tables

✅ Adjusts for your body shape and proportions, not just measurements

✅ Accounts for stretch, style cut, and even vanity sizing trends

✅ Shows accurate size matches across UK, US, and EU brands

✅ Free to use, no downloads—just input your details and shop confidently

Tellar vs Size Charts: What You Get

Feature	Brand Size Charts	Tellar.co.uk
Based on actual fit data	❌ No	✅ Yes
Considers body shape	❌ No	✅ Yes
Adjusts for fabric/cut	❌ Rarely	✅ Yes
Works across 1,500 brands	❌ No	✅ Yes
Free and browser-based	❌ Manual lookup needed	✅ One-click instant match

Try Tellar.co.uk Today

➡️ Create your free profile
➡️ Use the Store Size Lookup Tool
➡️ Download your free printable measuring tape
➡️ Explore the Fashion Hub: honest advice, style guides & real-world sizing truths

Tellar Fashion Hub: Go Beyond the Chart

Explore Tellar’s expert-written, unbiased guides:

Follow Tellar for Daily Fit Tips & Advice

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

Final Word

Size charts serve a purpose—but they’re no match for the complexity of real-world bodies and brand variation. Whether you're shopping high street or luxury, don’t rely solely on brand size charts. Use Tellar.co.uk to match your shape to the right size in any store, instantly and accurately.

Fit confidence starts here. It’s free. It’s easy. And it’s the future of fashion.