Last updated: Dec 29, 2024

mm to Ring Size Converter

Q: 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: Take a string and wrap it once around the finger you want to measure. Mark the string where it overlaps over itself. Using a ruler, measure the length of the string you marked. Check your ring supplier's chart for your ring size. 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.

Q: 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.

Created by Kenneth Alambra

Kenneth Alambra

Holds a Bachelor’s degree in Civil Engineering with 3+ years experience in fit-out construction and another 3+ years in technical sales. Ken has always been interested in creativity and innovation. He finds himself having fun solving problems and thinking of ways to improve anything he comes in contact with. During his free time, he plays a lot of bullet chess, listens to some pop music, or tries to learn something new – like preparing his favorite foods. See full profile

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Komal Rafay

A master's in Bioinformatics, with 3+ years of experience as a project manager. She has a vast experience of 7+ years in teaching Math, Computer science, and General Sciences, not only professionally but also to help out the children of the neighborhood. She is an enthusiastic reader with a thirst for knowledge who would even read the shampoo labels. As a side hustle that satisfies her love for art, she is a body art and henna expert. In her free time, you will find her reading books, writing short stories, playing with her pets, or experimenting with food while listening to some bouncy music. See full profile

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Table of contents

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 Other related ring-sizing tools FAQs

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.

Keep on reading to start discovering your fingers' ring sizes. 💍

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:

Illustration of how to measure a finger using a strip of paper and a ruler.

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.

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
Inside Diameter (mm)	Inside Circumference (mm)	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 7 (US).

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

FAQs

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:

Take a string and wrap it once around the finger you want to measure.
Mark the string where it overlaps over itself.
Using a ruler, measure the length of the string you marked.
Check your ring supplier's chart for your ring size.
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.