Measure the inside diameter of the ring (in mm) using a ruler or calipers
Use a printable ring-size chart and measure the inside diameter at the widest point
Measure your finger circumference with a flexible tape measure or string, then convert to size using a conversion chart
Use the “circumference to diameter” method: diameter (mm) = circumference (mm) ÷ 3.1416, then match diameter to a ring-size chart
If between sizes, choose the larger size for comfort or the smaller size for a snug fit
Measure at the end of the day when fingers are slightly larger, and avoid measuring in very cold temperatures
Measure more than once and average the results
If using a ring sizer tool, slide the correct size onto your finger until it fits comfortably and does not spin or pinch
Confirm with the correct standard system (US, UK, EU, JP) before finalizing the size