RingFit Gauge Measurement Disclaimer

What affects real-world fit

Actual ring fit varies with the manufacturer, the width of the ring band, finger swelling, temperature, the measurement method used, and the quality of your screen calibration. Fingers are typically largest at the end of the day and in warm weather, and smallest when cold.

How accurate RingFit can be

On a screen calibrated against a physical reference such as a bank card, RingFit resolves inner diameter to a fraction of a millimetre. One quarter of a US ring size is about 0.2 mm of diameter, so a careful calibration and a careful alignment matter more to your result than the arithmetic does. If your screen is not calibrated, RingFit says so and does not present a millimetre value as reliable.

Where charts disagree

The US, ISO/European, UK and Japanese systems have published definitions and RingFit follows them. Indian and Chinese sizes are marked as approximate in the app because trade charts for those markets differ meaningfully between sellers.

Before an expensive purchase

For engagement rings, custom or made-to-order pieces, or permanent resizing, confirm the final size with a professional jeweller. A jeweller can also account for band width and knuckle size in a way no on-screen measurement can.