# mm to Ring Size Converter

Created by Kenneth Alambra
Reviewed by Komal Rafay
Last updated: Jun 05, 2023

If you're finding a way to convert the circumference or diameter of a finger in millimeters to its corresponding ring size, then this mm-to-ring size converter is for you. With this calculator, you can find the correct ring size by measuring the length of a string or a strip of paper you can wrap around any of your fingers.

In this calculator, you will learn the following:

• How to find your ring size using this mm-to-ring size converter;
• How to determine the ring size using the mm-to-ring size chart; and
• Some frequently asked questions about the conversion from mm to ring size.

## How to find your ring size using this mm-to-ring size converter

You can easily determine your ring size by wrapping the knuckle of your finger using a non-stretchable string or a strip of paper and marking where one of its ends falls, as shown in the image below:

With a ruler, measure the length of that string or paper in millimeters and select the closest value available in the drop-down list of our mm-to-ring size converter's Inside circumference variable.

Our tool will display its corresponding US & Canada ring size and other equivalent ring sizes (used in UK & Australia, France & Russia, Germany, Switzerland, or Japan) if applicable.

If you want to find the ring size of another ring, you can measure its diameter by aligning it over a ruler from the zero mark to a reading on the ruler. Then, select the closest value available in the Inside diameter variable of our tool.

✅ Use our tool in advanced mode by clicking the Advance mode button below our tool if your ruler can only measure in inches.

## How to determine the ring size using the mm-to-ring size chart

After measuring your finger, you can also use the mm-to-ring size conversion chart below:

 Inside Diameter (mm) Inside Circumference (mm) Sizes UK & Australia US & Canada France Germany Japan Switzerland 11.53 36.22 _ 0 _ _ _ _ 11.95 37.54 A 1/2 _ _ _ _ 12.37 38.86 B 1 _ _ 1 _ 12.78 40.15 C 1 1/2 _ _ _ _ 13.21 41.50 D 2 41 1/2 13 1/2 2 1 1/2 13.61 42.76 E 2 1/2 42 3/4 13 3/4 3 2 3/4 14.05 44.14 F 3 44 14 4 4 14.36 45.11 G 3 3/8 45 1/4 _ 5 5 1/4 14.45 45.40 G 1/4 3 1/2< _ 14 1/2 _ _ 14.56 45.74 G 1/2 3 5/8 _ _ 6 _ 14.65 46.02 H 3 3/4 46 1/2 _ _ 6 1/2 14.86 46.68 H 1/2 4 _ 15 7 _ 15.04 47.25 I 4 1/4 47 3/4 _ _ 7 3/4 15.27 47.97 I 1/2 4 1/2 _ 15 1/4 8 _ 15.40 48.38 J 4 5/8 49 15 1/2 _ 9 15.70 49.32 J 1/2 5 _ 15 3/4 9 _ 15.80 49.64 K 5 1/8 50 _ _ 10 16.00 50.27 K 1/2 5 3/8 _ 10 _ 16.10 50.58 L 5 1/2 51 3/4 16 _ 11 3/4 16.51 51.87 M 6 52 3/4 16 1/2 12 12 3/4 16.92 53.16 N 6 1/2 54 17 13 14 17.35 54.51 O 7 55 1/4 17 1/4 14 15 1/4 17.75 55.76 P 7 1/2 56 1/2 17 3/4 15 16 1/2 18.19 57.15 Q 8 57 3/4 18 16 17 3/4 18.53 58.21 Q 3/4 8 1/2 _ 18 1/2 17 _ 18.61 58.47 R 8 5/8 59 _ _ 19 18.89 59.34 R 3/4 9 _ 19 18 _ 19.10 60.00 S 9 1/8 60 1/4 _ _ 20 1/4 19.41 60.98 S 3/4 9 1/2 _ 19 1/2 19 _ 19.51 61.29 T 9 5/8 61 1/2 _ _ 21 1/2 19.84 62.33 T 1/2 10 _ 20 20 _ 20.02 62.89 U 10 1/4 62 3/4 _ 21 22 3/4 20.20 63.46 U 1/2 10 1/2 _ 20 1/4 22 _ 20.32 63.84 V 10 5/8 63 _ _ 23 3/4 20.68 64.97 V 1/2 11 _ 20 3/4 23 _ 20.76 65.22 W 11 1/8 65 _ _ 25 21.08 66.22 W 3/4 11 1/2 _ 21 24 _ 21.18 66.54 X 11 5/8 66 1/4 _ _ 26 1/4 21.49 67.51 Y 12 67 1/2 21 1/4 25 27 1/2 21.89 68.77 Z 12 1/2 68 3/4 21 3/4 26 28 3/4 22.33 70.15 Z+1 13 _ 22 27 _

For example, you find out that you can wrap your finger with a 54.0 mm strip of paper end-to-end. From the chart above, the next inside circumference measurement of a ring size available is 54.51 mm. That means your finger ring size would be size 17 (US).

🙋 Remember that, since our knuckles are not perfectly round, we choose the next one and not the closest smaller ring size.

If you found our mm-to-ring size converter useful, perhaps you may also enjoy reading our other related tools listed below:

Read more useful tips for determining your proper ring size in our ring size converter. 😊

## FAQ

### How do I convert a millimeter measurement of my finger to a ring size?

To convert a measurement of your finger in millimeters to a ring size:

1. Take a string and wrap it once around the finger you want to measure.
2. Mark the string where it overlaps over itself.
3. Using a ruler, measure the length of the string you marked.
5. You can also divide the string's length by π or 3.14 if the supplier's chart asks for the equivalent diameter of your ring size.

### What ring size measures 16 mm in diameter?

The 5 3/8 US and Canada ring size has an inside diameter of 16 millimeters. In UK and Australia, find the size K 1/2 if your ring measures 16 millimeters in diameter.

Kenneth Alambra
Measurements
Inside circumference
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mm
Inside diameter
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mm
Ring size equivalents
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UK & Australia
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France & Russia
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Germany
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Switzerland
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Japan
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