Ring size chart and calculator
Commitment is easier when it fits.
Measure around your finger, or straight across the inside of a ring that already fits. We'll turn it into a US ring size, adjusted for wide bands and big knuckles the way jewelers do.
Built from the size charts of Wikipedia ring size table, GIA and Brilliant Earth.
By the Sizemaven team. Rules checked against their sources October 2026.
- 1MeasurementFor a finger, wrap a thin paper strip or non-stretch string around the base of the finger, mark where it overlaps, and measure that length. For a ring, measure straight across the inside at its widest point; measuring to the outside edge is the common mistake.
- 2Around the knuckleWrap the strip around the knuckle the same way. Skip it unless the knuckle is clearly bigger than the base of the finger.
Ring size chart
US sizes on the standard scale used by GIA and Wikipedia. Each half size adds 0.41 mm of diameter, and the ISO size is the inside circumference in mm.
| US size | Inside diameter | Inside circumference | ISO size |
|---|---|---|---|
| 3 | 14.1 mm | 44.2 mm | 44 |
| 4 | 14.9 mm | 46.8 mm | 47 |
| 5 | 15.7 mm | 49.3 mm | 49 |
| 6 | 16.5 mm | 51.9 mm | 52 |
| 7 | 17.3 mm | 54.4 mm | 54 |
| 8 | 18.1 mm | 57 mm | 57 |
| 9 | 18.9 mm | 59.5 mm | 60 |
| 10 | 19.8 mm | 62.1 mm | 62 |
| 11 | 20.6 mm | 64.6 mm | 65 |
| 12 | 21.4 mm | 67.2 mm | 67 |
| 13 | 22.2 mm | 69.7 mm | 70 |
| 14 | 23 mm | 72.3 mm | 72 |
| 15 | 23.8 mm | 74.8 mm | 75 |
Ring size guides
Questions about rings
How do I measure my ring size at home?
Wrap a thin strip of paper or non-stretch string around the base of the finger, mark where it overlaps, and measure the length in millimeters. GIA warns that string stretches and paper slips, and a 1 to 2 mm error is half a size to a whole size, so check with a ring sizer before buying a ring that cannot be resized.
How do I find my size from a ring I already own?
Measure the inside diameter of a round ring that fits the same finger. On the US scale, size 7 is 17.3 mm and each whole size adds 0.81 mm, so even a 1 mm ruler error is more than a whole size. Calipers or a printed circle chart are more precise.
Do wide bands need a bigger size?
Usually yes. Brilliant Earth advises at least half a size up for bands over 4 mm, and Blue Nile and GIA say wide bands fit tighter.
When should I measure?
Later in the day, at room temperature. GIA notes that fingers shrink in the cold and swell in the heat, and Brilliant Earth says fingers are largest at the end of the day.
What is the most common ring size?
Blue Nile reports 6 as the most popular women's size (5 to 7 most purchased) and 9 as the most popular men's size (8 to 10.5 most purchased). Brilliant Earth names 6 and 7 for women and 9 and 10 for men.
How we size rings
The rule comes from the charts below, checked October 2026. Brands differ, so check the size chart on the product page before you buy. Read our method