HELP & SUPPORT

TL;DR - Quick Start

WhatSize converts clothing sizes between brands. Pick a brand you want to buy from, tell us what size you wear in a brand you already own, and get your recommended size instantly. Works 100% offline, no account needed, $1.99 one-time purchase.

Getting Started

How to Convert a Size

  1. Choose the brand you want to buy from - Select FROM and pick the brand
  2. Enter what you currently own - Select a brand you own and your size in that brand
  3. Get your result - The app shows your recommended size with measurement comparison

Note: The app automatically saves each item you enter to "My Closet" for quick reference later.

Frequently Asked Questions

How accurate are the size conversions?
Very accurate! We use actual brand size charts and real body measurements (in centimeters). The app shows you the math behind each recommendation so you can see exactly how close the measurements are.
What if my brand isn't supported?
Email us at with the brand name. We prioritize new brand requests based on user demand and add them in regular updates.
Does the app work offline?
Yes! 100% offline. All size charts are bundled with the app, so you can use it anywhere - even on a plane or in a store with no signal.
How do I add items to My Closet?
Items are added automatically! Every time you complete a size calculation, the app saves your "source" item (the clothing you own) to My Closet. No manual entry needed.
Can I use the app in different languages?
Yes! WhatSize supports 8 languages: English, Nederlands, Español, Français, Deutsch, 日本語, 한국어, and 中文. Change the language in Settings and the entire app translates instantly.
What categories are supported?
Currently: Tops (shirts, hoodies, jackets, sweaters) and Bottoms (pants, jeans, shorts). More categories (dresses, shoes, accessories) are coming in future updates.
How do regional sizes work (US, UK, EU, etc.)?
When selecting a brand, you'll also choose the region (e.g., "Nike US" or "Nike UK"). This ensures you get the correct size labels that match where you're shopping. The app handles all the measurement conversions automatically.
Can I switch between CM and Inches?
Yes! Go to Settings and toggle between CM and Inches. All measurements throughout the app will update to your preferred unit.
Is my data private?
Absolutely. We collect ZERO data. Everything you save stays on your device. Read our full Privacy Policy.
How do I delete my saved items?
Go to Settings → Clear Data to remove all saved items from My Closet. You can also swipe left on individual items in My Closet to delete them one at a time.
What if I don't have a clothing item from a supported brand?
Use Quick Convert mode! Switch to Quick Convert at the top of the calculator. Simply select your region (US, UK, EU, etc.), choose your size category and gender, then enter a standard size (like "M" or "10"). The app will show you what that size means in all other regions - perfect for international shopping when you know your local size but need to shop abroad.

Note: Quick Convert uses general international sizing charts, not brand-specific data, so always double-check against the brand's size chart when possible.

Troubleshooting

The app isn't translating to my language

Go to Settings and manually select your preferred language. Make sure you're using one of the 8 supported languages.

I can't find a size for a brand

Some brands use different labeling systems by region or category. Make sure you've selected the correct region (US, UK, EU, etc.) and category (Tops vs Bottoms).

I can't find a brand in the search

Start typing the brand name - the list filters as you type. If the brand still doesn't appear, it may not be in our database yet. Request it via email!

Pro Tips

  • Use the measurement comparison - The result card shows the actual cm/inch measurements. If two sizes are close, you can decide based on your fit preference.
  • Build your closet first - Enter a few items you own that fit perfectly. Then you can quickly tap them to use as your "source" size.
  • Check multiple brands - If you're shopping at a new brand, compare it against 2-3 items you own to get a consensus.
  • Pay attention to variants - Some brands have Tall, Petite, or Plus sizing. Make sure you're comparing the right variants.

Still Need Help?

Email us at

We typically respond within 48 hours. Please include:

  • Your device model and iOS version
  • A clear description of the issue
  • Screenshots if applicable