Free Ring Size Calculator

Enter a fitting ring’s inner diameter or your finger’s circumference into the ring size calculator. Choose the correct unit and measurement method. The result is an estimate based on our sizing references; compare it with the seller’s chart before ordering.

Wrap a narrow, non-stretch paper strip around the base of your finger without squeezing. Mark the overlap, lay the strip flat, and measure from its starting edge to the mark. Enter that circumference in mm, cm, or inches. Repeat the measurement and check that the ring can pass your knuckle.

If 7 cm is the circumference around your finger, it equals 70 mm and corresponds to EU 70 under the circumference convention. It is approximately US 13, but not an exact match: our US 13 reference measures 69.74 mm around. A 70 mm circumference is just above this calculator’s supported measurement range. Confirm with a jeweler rather than forcing an out-of-range input. If you measured diameter instead, this conversion does not apply.

Seven inches equals 177.8 mm. If that is your measured finger circumference, it is far outside this tool’s ring-sizing range, so recheck what you measured and which units you used. Seven inches is not US ring size 7. In our reference, US 7 has an inside diameter of 17.30 mm and a circumference of about 2.1398 inches.

Yes, you can estimate the size of an existing ring using a calibrated phone screen. First match the calibration outline to a standard ID-1 bank card. Then place the ring lightly against the screen and match its inside edge to the circle. Reverify after changes to zoom or display settings. Placing a finger on the screen does not measure its circumference.

You need an existing reliable reference, such as a confirmed size for the same finger or a ring that fits it. A past purchase record may help if it identifies the sizing system and the fit is still right. Appearance, height, weight, or clothing size cannot establish an exact ring size.

Select the original sizing system and known size in the ring size converter. It compares inside diameters to find the closest supported US / Canada, UK / Australia, EU, India, and Japan equivalents. International results are approximate because reference conventions and size increments differ. Your seller’s own chart takes priority.

An ordinary photo without a trustworthy physical scale cannot reliably establish ring size. Perspective, camera distance, and finger shape affect the image, and visible finger width is not circumference. This website does not use AI camera measurement. Use a calibrated ring comparison, a measured paper strip, or a professional fitting instead.

There is no single normal ring size for women. Fit depends on the particular finger, hand, knuckle, and ring design, not gender alone. A retailer’s suggested average is not a measurement of your finger. Use your own measurement or a ring that fits, and check the sizing system before buying.

For a surprise gift, use a ring the person already wears on the intended finger, if you can borrow it with permission, or ask someone who knows their confirmed size. A ring from another finger may not fit. If you cannot obtain a reliable reference, consider a placeholder ring or discuss exchange and resizing options with the seller before purchasing.

If you already know a ring size, use the converter to look up an approximate equivalent in another system without taking a new measurement. If neither a confirmed size nor a fitting ring is available, any selection is a guess. Arrange a fitting or choose an option with an appropriate exchange policy.

A US size 7 is not inherently big or small for a woman; whether it fits depends on the finger. In this site’s reference, US 7 has a 17.30 mm inside diameter and about 54.35 mm circumference. The number 7 means something different in other sizing systems, so confirm that the label is US / Canada.

This site does not have a representative population dataset from which to calculate an average ring size for men. Retailer estimates vary by customer group, country, and finger. An average would not identify an individual’s fit anyway. Measure the intended finger or use a ring that already fits it.

In this calculator, US / Canada sizes advance in half-size steps from 3 to 13. UK / Australia uses the whole and half-letter entries available in our reference. EU sizes advance by 1 mm of circumference. India and Japan use their own reference entries. These increments are not interchangeable, and rounded diameter differences are not identical across every row.

Choose one of two methods: measure a fitting ring’s inside diameter, or measure your finger’s full circumference with a paper strip and ruler. For an on-screen circle, calibrate first. For a printable sizer, print at 100% / Actual size and verify the 50 mm check line. Repeat the measurement at a comfortable room temperature and consider knuckle fit.

Some charts list inside diameter; others list inside circumference. Conversion charts compare regional labels, such as US numbers, UK letters, EU circumference sizes, and India or Japan numbers. Printable charts add circles for physical comparison. Brand charts can use different conventions, so check the chart’s units, source, and intended product before using it.

To correct a calculator result, check the measurement method and units, then enter a new measurement or adjust the diameter controls. To change a physical ring’s fit, ask a jeweler whether its material and design allow resizing. Do not assume every ring can be resized, and avoid cutting or bending it yourself. Ask the manufacturer about fit options for smart rings.

Diameter is the straight distance across the inside of a ring. Circumference is the full distance around it and equals diameter multiplied by π. A paper strip wrapped around your finger measures circumference; a straight measurement across the ring opening measures diameter.

Select cm or inches in the finger circumference calculator and enter the full measured length. One centimeter equals 10 millimeters, and one inch equals 25.4 millimeters. The tool converts the length and compares sizing references. If your measurement is a diameter, convert it to millimeters and use the existing-ring input instead.

No. US sizes use numbers and UK sizes use letters, including supported half-letter steps. The converter shows approximate equivalents through inner diameter. Check the seller’s own chart because published references and brand conventions can differ.

Repeat the measurement and compare both neighboring fits. Consider your knuckle, band width, ring shape, and comfort. A larger size is not automatically better for everyone. Ask your jeweler to check the fit before buying an expensive or non-resizable ring.

No. Use the sizing kit for your exact Oura model. Smart-ring fit and size labels are not interchangeable with standard jewelry sizes.