Ring Sizer: Find Your Size

Measure a ring at true physical size, right on the screen. Calibrate once with any bank card, then lay a ring on the display and slide the circle until it meets the inside edge of the band.

HOW IT WORKS
• Match the on-screen outline to a bank card — every card is the same standard size
• Lay your ring on the screen and adjust the circle to the inside of the band
• Read out the US size and the inner diameter in millimetres
• Works fully offline — no account, no sign-up, nothing collected

Calibration is what makes the reading real: it teaches the app how large a millimetre is on your particular screen. Without calibrating, the size shown is only an estimate. Use it to narrow down a size, and confirm with a jeweller before you buy or resize a ring.

The free version covers the middle 7 US sizes and three readings a day. Pro opens all 21 sizes, adds EU, UK and Japanese conversions and saved sizes, and keeps your calibration saved between sessions.

Pro: unlimited use, all features unlocked. One-time purchase.