Ring size converter
Pick a ring size in one system to see it in the others, or enter a measurement in millimetres to find the closest size everywhere. The values are rounded approximations from widely used charts, so confirm important orders with a calibrated ring sizer.
Equivalent sizes
Values are rounded approximations based on widely used charts. Charts differ slightly between countries and jewelers, so confirm a final order with your jeweler or a calibrated ring sizer.
How to use the converter
Choose From a ring size to convert a size you already know. Select the size system, then the size, and the converter shows the equivalent US, UK, EU, Indian and Japanese sizes, along with the inner diameter and inner circumference in millimetres. When you switch systems, it keeps the same ring and picks the nearest size in the new system.
Choose From a measurement if you have measured a ring or a finger. Enter the inner diameter of a ring that fits, or the inner circumference in millimetres, and the converter finds the closest size in every system. Use Show the full size table to see every US size from 3 to 13 in half sizes next to its equivalents.
How the systems work
Every ring size describes the inside of the ring, either its diameter or its circumference.
- US and Canada use numbers with half and quarter sizes. Each whole size adds about 0.81 mm to the inner diameter, and a US 7 is about 17.3 mm across.
- UK, Ireland and Australia use letters from A upwards, with half sizes in between. Sizes beyond Z continue as Z+1, Z+2 and so on.
- EU and ISO sizes are simply the inner circumference in millimetres, so a size 54 measures about 54 mm around the inside.
- India and Japan use numbered scales that, on many charts, sit about 40 below the inner circumference in millimetres. The two line up closely for most sizes, although individual charts differ slightly.
Because each system steps in different increments, sizes rarely convert exactly. The converter rounds to the nearest size, so treat the neighbouring sizes as possible matches too.
How to measure accurately
- Measure a ring that fits. Lay a ruler across the inside of the ring at its widest point and read the inner diameter in millimetres.
- Measure the finger. Wrap a strip of paper around the base of the finger, mark where it overlaps and measure the length in millimetres. That is the circumference.
- Measure at the right time. Fingers are often smaller in the morning and in the cold, and larger later in the day or in the heat. Measure more than once.
- Allow for the knuckle. The ring has to pass over the knuckle, so if it is much wider than the base of the finger, choose a size between the two measurements.
- Allow for wide bands. Wide bands sit more snugly than narrow ones, so many jewelers suggest going up a quarter or half size for a wide band.
String is less reliable than paper because it stretches. For an engagement ring or an engraved band, a calibrated ring sizer at a jeweler is the safest choice.
Ring sizes and product images
Shoppers often struggle to judge how big a ring is from a photo alone. A scale shot on a hand, or next to a familiar object, answers that question before they ask. RenderMyJewels can turn a render into on-model images with its AI photoshoot, so customers see the ring worn before it is cast. See how to show jewelry scale for more ideas, and use the diamond size chart to compare centre stone sizes.
Sizes for different ring styles
The same finger can need slightly different sizes for different rings. Comfort fit bands, with a rounded inside, often feel looser than a flat band of the same size. Thick or heavy shanks feel tighter than slim ones. Rings with a large centre stone can turn on the finger if they are too loose, so many people choose a snug fit for solitaires. When in doubt, a jeweler can check the fit with sizers that match the band width.