How to measure ring size at home

Short answer: wrap a thin strip of paper or a non-stretch string around the base of the finger, mark where it overlaps, and measure that length in millimetres. That length is the inner circumference; divide by π to get the diameter, then convert to a size with the table below. A jeweler's finger gauge is still the most accurate option.^{[1 · Oct 29, 2026]}

A newly engaged couple laughing together on a rooftop at sunset as she shows her diamond ring

Method 1: string or paper strip

Cut a piece of string about 6 inches long, or a paper strip about 6 in × 1/4 in.^{[2 · Oct 29, 2026]}
Wrap it snugly around the base of the finger you will wear the ring on, below the knuckle, and mark the overlap.^{[2 · Oct 29, 2026]}
Check that it slides over your knuckle. If the knuckle is noticeably larger, Brilliant Earth suggests a size between the base and knuckle measurements.^{[3 · Oct 29, 2026]}
Measure the marked length in millimetres and use the table.
Repeat three times on different days; Jewelers Mutual recommends this because finger size changes.^{[2 · Oct 29, 2026]}

GIA cautions that string can stretch, paper can curl, and neither accounts for the knuckle, so treat a home result as an estimate.^{[1 · Oct 29, 2026]}

Method 2: measure a ring that already fits

Measure across the inside of the ring, edge to edge, in millimetres. That is the inner diameter; compare it with our ring size chart.

Circumference to US size

Measured length (circumference)	Diameter (C ÷ π)	Exact US size	Nearest half size
44 mm	14.01 mm	2.92	3
46 mm	14.64 mm	3.71	3.5
48 mm	15.28 mm	4.49	4.5
50 mm	15.92 mm	5.27	5.5
52 mm	16.55 mm	6.06	6
54 mm	17.19 mm	6.84	7
56 mm	17.83 mm	7.62	7.5
58 mm	18.46 mm	8.41	8.5
60 mm	19.10 mm	9.19	9
62 mm	19.74 mm	9.97	10
64 mm	20.37 mm	10.76	11
66 mm	21.01 mm	11.54	11.5
68 mm	21.65 mm	12.32	12.5
70 mm	22.28 mm	13.10	13

The math (our own arithmetic): d = C ÷ π, then US size = (d − 11.63) ÷ 0.8128, rearranged from the US/Canada formula.^{[4 · Oct 29, 2026]} Example: a 54 mm string gives d = 54 ÷ 3.1416 = 17.19 mm, and (17.19 − 11.63) ÷ 0.8128 = 6.84, so about a size 7.

Timing and conditions

Fingers shrink in the cold and swell in heat; GIA also mentions altitude and humidity.^{[1 · Oct 29, 2026]}
Jewelers Mutual suggests avoiding very hot or cold days, salty food, alcohol and exercise before measuring, and measuring midday.^{[2 · Oct 29, 2026]}
On a right-handed person, GIA says the left ring finger is typically about half a size smaller than the right.^{[1 · Oct 29, 2026]}
Between sizes, choose the larger: GIA notes it is easier to remove metal than add it.^{[1 · Oct 29, 2026]}

Sources: 1. GIA 4Cs, How to determine ring size. 2. Jewelers Mutual, How to measure ring size. 3. Brilliant Earth, How to measure ring size. 4. Wikipedia, Ring size. Checked Oct 29, 2026.