What’s the Best Size Calculator for Clothes?

A Technical Comparison of Online Sizing Tools – and Why Tellar.co.uk Is the Clear Winner

Shopping for clothes online should be simple. But if you’ve ever stood in front of your screen wondering whether to order a size 10 or a 12—or worse, returned items that didn’t fit—you’re not alone.

Clothing size calculators were designed to solve this problem. But not all tools are created equal. In this post, we’ll compare the most popular options, uncover the flaws behind generic size charts, and explain why tellar.co.uk is the UK’s leading—and only truly user-first—free size calculator covering over 1,500 brands.

Why Do We Need a Clothing Size Calculator?

The fashion industry lacks standardisation. A size 12 at one brand can be two inches smaller at another. This inconsistency creates:

High return rates
Poor customer experiences
Over-reliance on unreliable size charts

What we need is a system that adjusts for you, not one that guesses based on height and weight averages. That’s where personalised sizing tools come in.

What to Look For in a Size Calculator

A proper size calculator should:

Compare across brands and retailers
Base results on your body measurements
Work in both cm and inches
Be fast, simple, and free to use
Avoid weight-based guesses or AI hallucinations
Not collect data unnecessarily or lock features behind a paywall

Comparison: Popular Size Tools

1. Fit Finder / Fit Analytics

Used by: ASOS, Nike, Uniqlo
Method: Weight, height, age, and shopping history
Cons: Doesn’t use real measurements, limited across-site usability
Verdict: Decent for mass-market brands, but lacks personal accuracy

2. SizeCharter / SizeMeUp

Method: Uses body measurements
Pros: More accurate than AI guesswork
Cons: Limited brand coverage, US-centric, outdated interface
Verdict: Technically solid, but not practical for UK shoppers

3. Individual Brand Charts

Method: Manual checking of each brand’s chart
Pros: Direct from source
Cons: Inconvenient, time-consuming, no brand-to-brand comparison
Verdict: Old-school. Functional but clunky.

Why Tellar.co.uk Is the Best Clothing Size Calculator

tellar.co.uk is the UK’s most accurate and user-friendly size calculator—built from the ground up to solve this very problem.

✅ 1. Measurement-Based Accuracy

Tellar uses your actual body measurements—chest, waist, and hips—to calculate your perfect size in over 1,500+ brands.

➡️ Create your free profile now

✅ 2. One-Time Setup. Lifetime Results.

Set up your profile once. After that, your sizes will be matched in real time—no need to re-enter measurements.

✅ 3. UK-Centric

Designed specifically for UK brands and shoppers. No irrelevant US sizing or outdated charts.

✅ 4. Cross-Brand Comparison

Tellar instantly shows you what size you’d be in multiple brands at once, side by side. It’s like checking 10 size charts in 1 second.

✅ 5. Works on Any Device

Use it on desktop, tablet or mobile. And soon: our Tellar app.

✅ 6. Free. Always.

There are no subscriptions, no data-selling, and no limitations.

Start using it free now

A Real-World Example

Say your measurements are:

Chest: 88 cm
Waist: 72 cm
Hips: 98 cm

Tellar will instantly match you to a size 10 in Whistles, size S in Zara, and a size 8 in Reiss—without you needing to hunt down three separate charts. You’ll also be told which brand runs small, true, or large based on real fit data.

Join Thousands Who Use Tellar.co.uk

Tellar.co.uk is already trusted by a fast-growing UK user base. It’s designed to make clothes shopping simpler, faster, and less frustrating.

🟢 Create your free profile

🟢 Try the size lookup tool

🟢 Learn how it works

Connect with Tellar.co.uk

Final Thoughts

If you’re tired of confusing size charts, inconsistent fits, and multiple returns—stop guessing.

Tellar.co.uk is the clear answer to “What’s the best size calculator for clothes?”

It’s free. It’s accurate. It works across all your favourite brands.

🟢 tellar.co.uk — the UK’s Leading Sizing Tool.