US Ring Size Chart

How the US ring sizing scale works

The United States and Canada use a numeric scale that runs in half-size steps, typically from about size 3 up to size 13 for adults, though some jewelers stock quarter sizes for a finer fit. Each number corresponds to a specific inside circumference of the ring, measured in millimeters — the higher the number, the larger the ring's inner opening.

Unlike the UK's letter-based system or Japan's own numeric scale, the US system doesn't map directly onto a simple formula you can do in your head. It's a fixed reference table, standardized across US jewelers, which is exactly why a printed or digital chart is the fastest way to find your size — or to convert it into another country's system if you're ordering internationally.

US ring size chart

This chart shows the inside diameter and inside circumference behind each US size. If you already have a ring that fits, measuring its inside diameter against this table is one of the most reliable ways to confirm your size at home.

How to find your US ring size at home

1. Wrap a strip of string or paper snugly around the base of the finger you'll wear the ring on, mark where it overlaps, then lay it flat against a ruler in millimeters.
2. Match that circumference measurement against the chart above to find the closest US size.
3. If you already own a ring that fits well on that finger, measure straight across its inside edge instead — that's the diameter column in the chart.
4. Measure later in the day rather than first thing in the morning, since fingers are typically at their largest by evening — temperature and time of day genuinely affect the reading.

For a full walkthrough of every home method, including measuring an existing ring, see our complete measuring guide.

Half sizes, quarter sizes, and comfort fit

Most US jewelers stock half sizes as standard, and many offer quarter sizes for rings that need a very precise fit. If your measurement falls between two sizes on the chart, sizing up rather than down is usually the safer choice — a slightly loose ring can be resized smaller far more easily than a tight one can be resized larger.

Band width also affects fit at a given labeled size: wider bands (roughly 6mm and up) tend to sit more snugly than a thin band of the same size, so it's common to size up by a quarter or half size for a wide band, or to choose a comfort-fit inner edge, which makes any width easier to get on and off. If you're sizing a ring as a surprise, our engagement ring sizing guide covers how to get it right without asking.

Frequently asked questions