Ring size calculator
Find your ring size (US, European and others) from your finger circumference or from the inner diameter of a ring you already own.
How to useRing size calculator
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Ring size calculator: what it is for
Measure your finger with a string, or a ring you already own with a ruler, type the value in millimeters and see your US ring size, the European size (circumference in mm) and the inner diameter, with a full conversion chart.
Sizing can vary between jewelers: confirm the store's chart before buying.
How to use
- Choose circumference, diameter or a size you know.
- Type the measurement.
- See your size and the chart.
When to use it
- Buy an engagement ring as a surprise.
- Order a ring from an online store.
- Convert sizes from European stores.
Frequently asked questions
How do I measure my finger at home?
Wrap a piece of string or a strip of paper around the base of the finger, without squeezing. Mark where the end meets the rest, unroll it and measure it with a ruler in millimeters. That number is the circumference.
How do I measure with a ring I already have?
Lay the ring on a ruler and measure from one inner edge to the other, through the center. That is the inner diameter, in millimeters.
How do US ring sizes work?
US sizes go up in quarter steps: each whole size adds about 0.81 mm to the inner diameter. A US size 7 has an inner diameter of about 17.3 mm (54.4 mm around). Check the jeweler's chart, since some brands run slightly large or small.
Is it really free?
Yes, 100% free. No sign-up, no subscription and no usage limits. All Tools123 are free.