Ring Size Converter: US, UK, EU, JP
Ring sizes are a mess internationally — the US uses numbers, the UK uses letters, the EU uses millimeters of circumference, and Japan uses its own numbers. Order from an overseas seller with the wrong conversion and the ring will not fit.
This free converter translates between all four systems instantly. Enter your size in whichever system you know, and get the exact US, UK, EU, and Japanese equivalents — plus the inside diameter and circumference in millimeters, which is what jewelers actually measure.
Ring Size Converter
Enter your ring size in any system — get the exact equivalent in US, UK, EU, and Japanese sizes.
Your size in every system
| System | Size |
|---|---|
| US | |
| UK | |
| EU (French) | |
| Japanese |
Sizes vary slightly between makers — if you’re between sizes, go up for wide bands and down for thin bands. Measure at the end of the day when fingers are at their largest.
As an Amazon Associate we earn from qualifying purchases.
Frequently asked questions
How do I measure my ring size at home?
The most reliable DIY method is a plastic ring sizer gauge — cheap and reusable. In a pinch, wrap a strip of paper around your finger, mark where it overlaps, and measure the length in millimeters; that is your EU/French size.
Should I size up or down if I’m between sizes?
Go up for wide bands (they fit tighter) and down for thin, delicate bands. If your knuckle is much bigger than the base of your finger, size for the knuckle.
Why does my ring fit differently in summer and winter?
Fingers swell in heat and shrink in cold — sometimes by half a size or more. Always measure at the end of the day when your fingers are at their largest.
Are US and UK ring sizes the same?
No — the US uses a numbered scale (roughly 4–13) while the UK uses letters (roughly I–Z). For example, US 6 equals UK M1/2.
What does EU ring size mean?
EU (French) sizes are simply the inside circumference of the ring in millimeters — a size 52 ring measures 52 mm around the inside.