How to Measure Ring Size

Which method should you use?

If you are buying a ring that cannot be resized, use the home result as a starting point and confirm fit with the retailer or a jeweler. A visible-width estimate, a paper wrap and a physical finger gauge do not provide the same evidence.

Measure without a ring: use your phone

1. Open finger mode on your phone. Supported Android models set up automatically. An iPhone may match a screen configuration rather than an exact model. Check the scale label; a preview is only an example.
2. Keep the display upright at normal page scale. If automatic setup fails, select your exact supported model. Do not choose a similar-looking phone just to continue.
3. Rest the intended finger lightly between the guides. Place the base where the ring will sit, look straight down and avoid flattening the finger against the glass.
4. Match the visible sides. Move a handle or use the slider and fine-adjustment buttons. Lift your finger and repeat the alignment to check whether you get a similar reading.
5. Confirm to see the estimate. You can record the knuckle width separately. Read the method beside the result before saving its PNG card.

The phone method treats width as an equivalent circular diameter. It does not measure around your finger, and the screen presets and finger method have no validated physical tolerance. See exactly how the estimate is made.

Measure an existing ring’s inner diameter

Choose a round ring that fits the intended finger on the intended hand. A ring from another finger may have a different fit. Lay it flat and measure the inside edge to inside edge through its centre.

In on-screen ring mode, set the screen scale first, then adjust the gold circle so its outside edge matches the ring’s inside opening. If using a physical ruler, enter the inner diameter in the converter. A distorted or oval ring needs a different fit check.

For example, 17.3 mm of inner diameter maps to US 7 in our reference. Keep the original reading when comparing another seller’s chart; conversions are approximate.

Measure around your finger with paper

You need a narrow paper strip, a pen and a ruler. Wrap the strip at the ring’s intended position, mark where the end overlaps, then lay the strip flat. Measure from the starting end to the mark in millimetres. Enter that full length as circumference, not diameter.

Repeat without pulling the paper tight or leaving a gap. Check how the loop passes the knuckle. Paper can bend and compress differently from a rigid band, so use the reading as a guide. A paper strip without a ruler or a verified printed scale does not supply a length measurement.

For a 54 mm circumference, the circular equivalent is 54 ÷ π ≈ 17.19 mm in diameter. The converter selects the nearest reference row, not a custom ring size. Tiffany’s sizing guide also describes measuring a wrap and an existing ring.

Check the result before choosing a ring

A ring should sit comfortably and pass over the knuckle. Record which hand and finger you measured, keep the raw reading, and repeat if the alignment or paper tension was uncertain. Band width and the specific design matter; we do not apply one universal extra half size.

Use the full size chart to compare references, then check the seller’s own chart and fitting advice. The useful final result is a ring that fits your finger and joint, rather than a number with extra decimal places.

References: GIA’s explanation of fit and ring sizing; Tiffany’s measurement instructions. Phone steps describe this website’s own implementation and its current limitations.