Convert Circumference In Inches (in) to Diameter In Inches (in), Inner Diameter And Circumference Of A Ring

Ring size conversion page helps to convert jewelry ring sizes used around the globe. As you could probably expect, people use different scales to mark ring sizes in various parts of the world. This is not a problem though, our converter lets you instantly convert a ring size from any scale to all the others.

Ring sizes can be measured by inner diameter of a ring or by the length of the inner circumference of a ring.

Unlike many other ring conversion tables you can find on the web, we use formulas to calculate exact conversions based on official standards instead of providing a loose approximate matching. We want to make sure you get the most reliable conversion result.

For most systems we round up sizes to a quarter of a size step. If this rounding-up adds difference of more than 1%, we show the actual difference as a percent of the ring diameter. It may sound cumbersome, but it's easy. Just try it – enter any ring size and get it converted to all other sizes.

Circumference in inches (in)
Inner Diameter and Circumference of a Ring
Diameter in inches (in)
Inner Diameter and Circumference of a Ring

This page features online conversion from Circumference in inches to Diameter in inches. These units belong to the same measurement system: Inner Diameter And Circumference Of A Ring.

If you need to convert Circumference in inches to another compatible unit, please pick the one you need on the page below. You can also switch to the converter for Diameter in inches to Circumference in inches.

Other Units the Values Above Are Equal To

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Inner Diameter and Circumference of a Ring

These measurements represent size of a ring regardless of any national scale. Referring to a diameter or a circumference of a ring in inches or millimeters is the most reliable way to check the size.
Units: Diameter in inches (in)  / Diameter in millimeters (mm)  / Circumference in inches (in)  / Circumference in millimeters (mm)
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Ring Sizes in the United States, Canada and Mexico

Ring sizes in this scale are numerical starting from zero with quarter and half sizes. An increase of a full size adds roughly ⅒ inch in inside circumference of the ring. Sizes smaller than 0 are marked 00, 000, etc.

Please enter partial sizes like this: 5 1/2 or 10 1/4.

Units: Northern American ring size
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Ring Sizes in the United Kingdom, Ireland, Australia, New Zealand, and South Africa (Wheat Sheaf)

Wheat Sheaf is the commonly known gauge for measuring ring sizes in the UK. The official name is British Standard 1283:1945, later in 1987 replaced by British Standard 6820:1987. The wheatsheaf sizes use letters from A to Z, then Z+1, Z+2, etc. with half and quarter-sizes. In the old standard an increase of a full size used to add 1/64th of an inch in ring diameter. The new standard of 1987 redefined the sizes to be based on metric units, now an increase of a full size adds 1.25 mm of an inner circumference. The good news is the old and the new standards are in practice virtually the same.

The smallest possible ring size is A, it corresponds to ring inner circumference of 37.5 mm. For even smaller circumference lengths we still display size A with the percent difference, e.g. A [-10%].

Please enter partial sizes like this: C 1/2 or Z+3 1/4.

Units: Wheat Sheaf (UK, Ireland, Australia, South Africa)
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European Standard Sizes (ISO 8653:2016, most European countries)

This is the official system for measurement of rings that is set as a European standard. It is used in many European countries including France, Germany, Austria, Belgium, Finland, Sweden.

This system defines ring size to be equal to its inner circumference in millimeters.

Units: European ring size (ISO)
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Ring Sizes in Italy, Spain, Switzerland, the Netherlands, Brazil, India

A few European and South American countries as well as India use another system of sizes. They subtract 40 from the length of the ring circumference in millimeters to get the ring size.

The minimal ring size 0 in this scale corresponds to circumference length of 40 millimeters. For even smaller circumference lengths we still display size 0 with the percent difference, e.g. 0 [-10%].

Units: Ring size in Italy, Spain, Switzerland, the Netherlands, Brazil, India
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Old Brazilian Ring Sizes

In addition to European ISO 8653 and alternative European scale, an older system of ring sizes is widely used across the country of Brazil.

The minimal ring size 1 in this scale has inner diameter of 11.8 millimeters. Each size increments the diameter by 0.35 millimeters.

Units: Older Brazilian ring size
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Ring Sizes in Russia, Ukraine, Belarus and Other ex-USSR Countries

These countries use inner diameter of a ring in millimeters as it's size. In Russia it is officially defined by Russian Standard 117-3-002-95 of 1988.

Some sources say these sizes may also be occasionally used in Germany and Austria.

Units: Ring size in Russia, Ukraine, Belarus
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Ring Sizes in Japan, China, Korea, Hong Kong, Taiwan, Singapore

Many Asian countries use system of sizes that is based on ring diameter starting with size 1 at 13 mm and increasing ⅓ of mm with each size. For rings with smaller diameters we still display ring size 1 with the percent difference, e.g. 1 [-10%].

Units: Asian ring size

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