About RingSize

RingSize is a free online ring size calculator that helps you measure your ring size at home. We built it because many people guess their size, order a ring online and then deal with returns and resizing fees.

What the tool does

RingSize turns your phone screen into a ruler. You calibrate the screen with a bank card, then either match a circle to a ring that fits or match a line to a strip of paper wrapped around your finger. The result is shown in US, UK, EU, Indian and Japanese ring sizes, along with the inner diameter and circumference in millimetres.

Privacy by design

The measurement runs entirely in your browser. We do not upload or store the measurements you make.

How we write our guides

Our ring size chart and guides are written to be practical and easy to follow. We use standard sizing formulas and widely published conversion tables, and we say clearly when a conversion is approximate. If you spot a mistake, please tell us through the contact page and we will review it.

Important note

RingSize provides estimates. Ring sizing can vary by brand, band width and style. For valuable rings, confirm the size with a jeweler.