Ring Size Chart & Finder

Quick answer: your ring size is the inside of the ring. A US size 7 is 17.3 mm across and 54.3 mm around inside (GIA), a UK N or N½ depending on the jeweller, an EU 54.5 and a Japanese 14. Each US size up adds about 0.8 mm across. GIA prefers measuring a ring that already fits over string or paper: this page draws true-size circles on your screen to lay it on, or prints them.

How to use it

Pick how you want to measure. A ring I own: lay it on the screen and change the size until the circle sits just inside the ring’s inside edge; check the screen first with a US quarter or a ruler, because screens are not all the same size. My finger: type the length of a string or paper strip that went around it. A size I know: pick a US, UK, European or Japanese size to see the others. The answer shows the same ring on GIA’s, Brilliant Earth’s and Tiffany’s charts, because they do not print the same UK and Japanese names. You can also print a sizer: circles at true size with a line to check the print.

The ring size chart

From GIA’s ring size chart, Brilliant Earth’s and Tiffany’s. They agree on the millimetres to a few tenths; they are half a letter apart on UK sizes (GIA calls a US 7 an N, Brilliant Earth an N½), so check the letter against the shop’s own chart. European sizes are the inside circumference in millimetres. GIA’s table prints “1.5” between I and J at US 4¾, a typo for I½.

Three ways to measure

• A ring that fits: the most reliable at home. “Place it over the printed circles until the inside edge of your ring lines up perfectly with one of the circles” (Blue Nile). On screen, check the scale first: a US quarter is 0.955 in (24.26 mm) across (U.S. Mint).
• A string or paper strip: wrap it around the base of the finger, mark where it meets, and “Lay the string on a flat surface and use a ruler to measure the length (in inches or millimeters) up to the mark” (Tiffany). GIA warns: “Both methods lead to inaccuracies: String can stretch and paper can be easily damaged”, and they do not check the knuckle.
• A printed sizer: print at 100% and check the scale: “A reference line is included to confirm the chart is printed to scale in millimeters (mm)” (Blue Nile). Brilliant Earth: “Set page scaling to “100” in your print settings and use 8.5 x 11-inch standard paper.”

Three worked examples

A ring that fits matches the US 7 circle: US size 7, 17.3 mm across inside, UK N (GIA) or N½ (Brilliant Earth), EU 54.5, Japan 14.

A paper strip 57 mm long: US size 8 (56.9 mm around on GIA’s chart), UK P or P½, EU 57.

A European size 52: US size 6, 16.5 mm across; Japan 11 on GIA’s chart but 12 on Brilliant Earth’s.

Before you order

• Over the knuckle: “The perfect size will be snug enough not to slip off but loose enough to slide over the knuckle without too much resistance” (Brilliant Earth).
• When to measure: “The most reliable time to measure is toward the middle or end of the day, when your fingers are at their largest” (Brilliant Earth); “Fingers shrink in the cold and swell in the heat” (GIA).
• Between two sizes: “If you are between sizes, opt for the larger size” (Tiffany; Blue Nile agrees).
• A wide band: “Since wider styles can feel tighter, consider going up half a size for a better fit” (Blue Nile); GIA: “Rings with wide shanks usually need to be a bit larger, as they will fit more snugly.”

Common mistakes

• Measuring the outside of the ring. The size is the inside edge.
• Trusting an unchecked screen or print. Screens differ; check the circle against a quarter or ruler, and the printed line against a ruler.
• Measuring cold hands first thing in the morning. Fingers are smaller then.
• Reading a UK letter off the wrong chart. Jewellers differ by half a letter; use the shop’s own chart.

More on Needle Style

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Sizes from GIA, Brilliant Earth and Tiffany; measuring advice from GIA, Blue Nile, Brilliant Earth and Tiffany; the quarter from the U.S. Mint. Checked 2026-09-28.

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