Measuring your ring size at home
The most reliable way is to measure a ring that already fits. Four steps, a ruler and a little care.
Key points
- Measure the inside of a ring that already fits the same finger on the same hand.
- Take two readings a quarter turn apart, use the average, and match it on our size chart.
- Go up a quarter to half a size for a band wider than about 4 mm.
In this article
Each full US ring size adds about 0.81 mm to the inside diameter, so half a size is about 0.4 mm. Small measuring errors add up quickly, which is why measuring a ring that already fits beats guessing.
Pick a ring that fits the right finger
Use a ring that fits the finger you plan to wear the new ring on, on the same hand. Fingers on your dominant hand are often slightly larger, and the same finger on each hand can differ by half a size. The ring should slide over the knuckle with a little resistance and should not spin freely once it is on.
Measure the inside diameter
Lay the ring on a ruler marked in millimeters and measure across the inside, from inner edge to inner edge, at the widest point. Then turn the ring a quarter turn and measure again. Rings that have been worn for a while are often slightly oval; if the two readings differ, use the average.
Match it to a size
US sizes follow a simple rule: the inside diameter in millimeters is about 11.63 plus 0.8128 times the size. A ring 17.3 mm across is a size 7, and one 16.5 mm across is a size 6. Our size chart lists every half size from 4 to 10 with its diameter and circumference.
Allow for width and warmth
A wide band covers more of the finger and feels tighter than a slim band of the same size. If the ring you measured is slim and the new one is wider than about 4 mm, go up a quarter to half a size.
Fingers also change through the day. They shrink in the cold and swell in heat, after exercise and by the evening. A ring sized on a cold morning can be tight by dinner, so measure at room temperature, later in the day.
No ring to measure
Paper strips and string stretch and slip, and they can easily read half a size or more out. A set of metal sizing gauges, like the ones at the top of this page, is more reliable, and any jeweler can size your finger in a minute. If a ring from us does not fit, the first resize within 60 days is free.
Filed under Care and buying · May 11, 2026
