Hey Product Hunt 👋 I built RingSizeCharts because I did the thing everyone does: ordered a ring online, guessed the size, and got it wrong. Size charts already exist. The problem is they're scattered, they contradict each other, and half of them assume you own a jeweller's sizer. So the tool does three things: 📏 Measure with nothing — a string, a strip of paper, or the inner diameter of a ring you already own. Plus a printable sizer at 100% scale. 🌍 Convert once — one measurement gives you US, UK, EU, Japan and China sizes together, in mm and inches, in both directions. 📖 Understand the gap — a full half-size chart, plus notes on how temperature and band width change the size you need. It started as a bare converter: one input, one number. But the questions people actually asked weren't about the number. They were "am I measuring this right?", "why is my size different in winter?". So it grew into a reference - the guides, the chart, the notes. Then I added the style collections, because the other half of the decision isn't the size, it's which ring. Three things I care about: nothing is uploaded (it all runs in your browser), it follows ISO 8653:2016, and it's in nine languages. Free, no sign-up. Two questions I'd love your take on: 1. Is there a size standard or region you'd want covered that isn't there yet? 2. If you've bought a ring online, what made the size feel risky? Thanks for taking a look 🙏

RingSizeCharts

Measure your ring size at home: US, UK, EU, Japan, China.

Measure your ring size at home: US, UK, EU, Japan, China.