How to convert cm to a ring size?

In order to convert centimeters or milimeters to a ring size you need to know what you have measured. A ring is a circle and a circle can be described by the diameter (or radius) and by the circumference. It is important to know what you have measured. If you measured the Diameter you can covert that to circuference as follows: Circumference = π x Diameter  (Where π  is pi which is 3.141).

Circle Diameter Radius Circumference To convert easily cm to a ring size use our online ring sizer converter which you can find on this page:

The measured size can be converted to an USA ring size or to UK, Japan or Euro ring size. Select what you have measured if it is in millimeters , centimeters or inches. Now select if it was the diameter or the circumference, finally select to which ring size you want it converted.

How to measure the ring finger size?

A professional jeweler can determine your proper ring size using a set of gauge rings. Other methods such as measuring a strip of paper around the finger can be inaccurate. It’s advisable to visit several jewelers at different times during the day.

Fingers will naturally swell in the morning and shrink in the evening. Other factors including temperature, humidity, and exercise can also temporarily change finger size. Wider bands can generally be worn looser. Someone with larger knuckles can wear a looser ring, while slimmer knuckles will require a tighter ring.

Most rings can be resized, however rings made of titanium are very difficult to resize.

Swiss Ring Sizes

Swiss Ring size compared to the International ring sizes, comparison guide. In the European Union (excluding the United Kingdom), ring sizes are specified using a numerical scale, that only has whole sizes.

  • In  Switserland, ring sizes are specified using a numerical scale, with quarter and half sizes.

The ISO standard for ring sizes is ISO 8653:1986, which defines standard ring sizes in terms of the inner circumference of the ring measured in millimetres.

Swiss
Inside Diameter
Inside Circumference
(inches)
mm
(inches)
mm
0.458
11.633
1.438
36.528
0.466
11.836
1.463
37.166
0.474
12.04
1.488
37.804
0.482
12.243
1.513
38.442
0.49
12.446
1.539
39.08
0.498
12.649
1.564
39.718
0.506
12.852
1.589
40.357
0.514
13.056
1.614
40.995
1.5
0.522
13.259
1.639
41.633
0.53
13.462
1.664
42.271
2.75
0.538
13.665
1.689
42.909
0.546
13.868
1.714
43.547
4
0.554
14.072
1.74
44.185
5.25
0.562
14.275
1.765
44.823
0.57
14.478
1.79
45.461
6.5
0.578
14.681
1.815
46.099
0.586
14.884
1.84
46.737
7.75
0.594
15.088
1.865
47.375
0.602
15.291
1.89
48.013
9
0.61
15.494
1.915
48.651
0.618
15.697
1.941
49.289
10
0.626
15.9
1.966
49.927
0.634
16.104
1.991
50.565
11.75
0.642
16.307
2.016
51.203
12.75
0.65
16.51
2.041
51.841
0.658
16.713
2.066
52.479
14
0.666
16.916
2.091
53.117
0.674
17.12
2.116
53.756
15.25
0.682
17.323
2.141
54.394
0.69
17.526
2.167
55.032
16.5
0.698
17.729
2.192
55.67
0.706
17.932
2.217
56.308
17.75
0.714
18.136
2.242
56.946
0.722
18.339
2.267
57.584
0.73
18.542
2.292
58.222
19
0.738
18.745
2.317
58.86
0.746
18.948
2.342
59.498
20.25
0.754
19.152
2.368
60.136
0.762
19.355
2.393
60.774
21.5
0.77
19.558
2.418
61.412
0.778
19.761
2.443
62.05
0.786
19.964
2.468
62.688
22.75
0.794
20.168
2.493
63.326
0.802
20.371
2.518
63.964
0.81
20.574
2.543
64.602
25
0.818
20.777
2.569
65.24
0.826
20.98
2.594
65.878
0.834
21.184
2.619
66.517
27.5
0.842
21.387
2.644
67.155
0.85
21.59
2.669
67.793
28.75
0.858
21.793
2.694
68.431
0.866
21.996
2.719
69.069
0.874
22.2
2.744
69.707
0.882
22.403
2.769
70.345
0.89
22.606
2.795
70.983
0.898
22.809
2.82
71.621
0.906
23.012
2.845
72.259
0.914
23.216
2.87
72.897
0.922
23.419
2.895
73.535
0.93
23.622
2.92
74.173
0.938
23.825
2.945
74.811
0.946
24.028
2.97
75.449
0.954
24.232
2.996
76.087
0.962
24.435
3.021
76.725
0.97
24.638
3.046
77.363

Japanese Ring Sizes

Japanese Ring size compared to the International ring sizes, comparison guide. There are several systems for denoting the sizes of jewellery rings in use around the world:

  • In Japan, ring sizes are specified using a numerical scale, that only has whole sizes.

The ISO standard for ring sizes is ISO 8653:1986, which defines standard ring sizes in terms of the inner circumference of the ring measured in millimetres.

Japan
Inside Diameter
Inside Circumference
(inches)
mm
(inches)
mm
0.458
11.633
1.438
36.528
0.466
11.836
1.463
37.166
0.474
12.04
1.488
37.804
0.482
12.243
1.513
38.442
1
0.49
12.446
1.539
39.08
0.498
12.649
1.564
39.718
0.506
12.852
1.589
40.357
0.514
13.056
1.614
40.995
2
0.522
13.259
1.639
41.633
0.53
13.462
1.664
42.271
3
0.538
13.665
1.689
42.909
0.546
13.868
1.714
43.547
4
0.554
14.072
1.74
44.185
5
0.562
14.275
1.765
44.823
0.57
14.478
1.79
45.461
6
0.578
14.681
1.815
46.099
7
0.586
14.884
1.84
46.737
0.594
15.088
1.865
47.375
8
0.602
15.291
1.89
48.013
0.61
15.494
1.915
48.651
9
0.618
15.697
1.941
49.289
0.626
15.9
1.966
49.927
10
0.634
16.104
1.991
50.565
0.642
16.307
2.016
51.203
11
0.65
16.51
2.041
51.841
12
0.658
16.713
2.066
52.479
13
0.666
16.916
2.091
53.117
0.674
17.12
2.116
53.756
14
0.682
17.323
2.141
54.394
0.69
17.526
2.167
55.032
15
0.698
17.729
2.192
55.67
0.706
17.932
2.217
56.308
16
0.714
18.136
2.242
56.946
0.722
18.339
2.267
57.584
17
0.73
18.542
2.292
58.222
0.738
18.745
2.317
58.86
18
0.746
18.948
2.342
59.498
0.754
19.152
2.368
60.136
19
0.762
19.355
2.393
60.774
0.77
19.558
2.418
61.412
20
0.778
19.761
2.443
62.05
21
0.786
19.964
2.468
62.688
22
0.794
20.168
2.493
63.326
0.802
20.371
2.518
63.964
23
0.81
20.574
2.543
64.602
0.818
20.777
2.569
65.24
24
0.826
20.98
2.594
65.878
0.834
21.184
2.619
66.517
25
0.842
21.387
2.644
67.155
0.85
21.59
2.669
67.793
26
0.858
21.793
2.694
68.431
0.866
21.996
2.719
69.069
27
0.874
22.2
2.744
69.707
0.882
22.403
2.769
70.345
0.89
22.606
2.795
70.983
0.898
22.809
2.82
71.621
0.906
23.012
2.845
72.259
0.914
23.216
2.87
72.897
0.922
23.419
2.895
73.535
0.93
23.622
2.92
74.173
0.938
23.825
2.945
74.811
0.946
24.028
2.97
75.449
0.954
24.232
2.996
76.087
0.962
24.435
3.021
76.725
0.97
24.638
3.046
77.363

International Ring Sizes

Overview of international ring sizes in a comparison guide. There are several systems for denoting the sizes of jewellery rings in use around the world:

  • In the United States and Canada, ring sizes are specified using a numerical scale, with quarter and half sizes.
  • In the United Kingdom, Ireland, and Australia, ring sizes are specified using an alphabetical scale, with half sizes.
  • In the European Union (excluding the United Kingdom), ring sizes are specified using a numerical scale, that only has whole sizes.
  • In Japan, ring sizes are specified using a numerical scale, that only has whole sizes.
  • In  Switserland, ring sizes are specified using a numerical scale, with quarter and half sizes.

The ISO standard for ring sizes is ISO 8653:1986, which defines standard ring sizes in terms of the inner circumference of the ring measured in millimetres.

United States
Inside Diameter
Inside Circumference
United Kingdom,
Japan
Swiss
Canada
(inches)
mm
(inches)
mm
Ireland,
Australia
0
0.458
11.633
1.438
36.528
1/4
0.466
11.836
1.463
37.166
1/2
0.474
12.04
1.488
37.804
A
3/4
0.482
12.243
1.513
38.442
A 1/2
1
0.49
12.446
1.539
39.08
B
1
1 1/4
0.498
12.649
1.564
39.718
B 1/2
1 1/2
0.506
12.852
1.589
40.357
C
1 3/4
0.514
13.056
1.614
40.995
C 1/2
2
0.522
13.259
1.639
41.633
D
2 1.5
2 1/4
0.53
13.462
1.664
42.271
D 1/2
2 1/2
0.538
13.665
1.689
42.909
E
3 2.75
2 3/4
0.546
13.868
1.714
43.547
E 1/2
3
0.554
14.072
1.74
44.185
F
4 4
3 1/4
0.562
14.275
1.765
44.823
F 1/2
5 5.25
3 1/2
0.57
14.478
1.79
45.461
G
3 3/4
0.578
14.681
1.815
46.099
G 1/2
6 6.5
4
0.586
14.884
1.84
46.737
H
7
4 1/4
0.594
15.088
1.865
47.375
H 1/2
7.75
4 1/2
0.602
15.291
1.89
48.013
I
8
4 3/4
0.61
15.494
1.915
48.651
J
9
5
0.618
15.697
1.941
49.289
J 1/2
9
5 1/4
0.626
15.9
1.966
49.927
K
10
5 1/2
0.634
16.104
1.991
50.565
K 1/2
10
5 3/4
0.642
16.307
2.016
51.203
L
11.75
6
0.65
16.51
2.041
51.841
L 1/2
11 12.75
6 1/4
0.658
16.713
2.066
52.479
M
12
6 1/2
0.666
16.916
2.091
53.117
M 1/2
13 14
6 3/4
0.674
17.12
2.116
53.756
N
7
0.682
17.323
2.141
54.394
N 1/2
14 15.25
7 1/4
0.69
17.526
2.167
55.032
O
7 1/2
0.698
17.729
2.192
55.67
O 1/2
15 16.5
7 3/4
0.706
17.932
2.217
56.308
P
8
0.714
18.136
2.242
56.946
P 1/2
16 17.75
8 1/4
0.722
18.339
2.267
57.584
Q
8 1/2
0.73
18.542
2.292
58.222
Q 1/2
17
8 3/4
0.738
18.745
2.317
58.86
R
19
9
0.746
18.948
2.342
59.498
R 1/2
18
9 1/4
0.754
19.152
2.368
60.136
S
20.25
9 1/2
0.762
19.355
2.393
60.774
S 1/2
19
9 3/4
0.77
19.558
2.418
61.412
T
21.5
10
0.778
19.761
2.443
62.05
T 1/2
20
10 1/4
0.786
19.964
2.468
62.688
U
21
10 1/2
0.794
20.168
2.493
63.326
U 1/2
22 22.75
10 3/4
0.802
20.371
2.518
63.964
V
11
0.81
20.574
2.543
64.602
V 1/2
23
11 1/4
0.818
20.777
2.569
65.24
W
25
11 1/2
0.826
20.98
2.594
65.878
W 1/2
24
11 3/4
0.834
21.184
2.619
66.517
X
12
0.842
21.387
2.644
67.155
X 1/2
25 27.5
12 1/4
0.85
21.59
2.669
67.793
Y
12 1/2
0.858
21.793
2.694
68.431
Z
26 28.75
12 3/4
0.866
21.996
2.719
69.069
Z 1/2
13
0.874
22.2
2.744
69.707
27
13 1/4
0.882
22.403
2.769
70.345
Z1
13 1/2
0.89
22.606
2.795
70.983
13 3/4
0.898
22.809
2.82
71.621
Z2
14
0.906
23.012
2.845
72.259
Z3
14 1/4
0.914
23.216
2.87
72.897
14 1/2
0.922
23.419
2.895
73.535
Z4
14 3/4
0.93
23.622
2.92
74.173
15
0.938
23.825
2.945
74.811
15 1/4
0.946
24.028
2.97
75.449
15 1/2
0.954
24.232
2.996
76.087
15 3/4
0.962
24.435
3.021
76.725
16
0.97
24.638
3.046
77.363

British UK Ring Sizes

British UK Ring size compared to the International ring sizes, comparison guide. There are several systems for denoting the sizes of jewellery rings in use around the world:

  • In the United Kingdom, Ireland, and Australia, ring sizes are specified using an alphabetical scale, with half sizes.

The ISO standard for ring sizes is ISO 8653:1986, which defines standard ring sizes in terms of the inner circumference of the ring measured in millimetres.

United Kingdom,
Inside Diameter
Inside Circumference
Ireland,
(inches)
mm
(inches)
mm
Australia
0.458
11.633
1.438
36.528
0.466
11.836
1.463
37.166
A
0.474
12.04
1.488
37.804
A 1/2
0.482
12.243
1.513
38.442
B
0.49
12.446
1.539
39.08
B 1/2
0.498
12.649
1.564
39.718
C
0.506
12.852
1.589
40.357
C 1/2
0.514
13.056
1.614
40.995
D
0.522
13.259
1.639
41.633
D 1/2
0.53
13.462
1.664
42.271
E
0.538
13.665
1.689
42.909
E 1/2
0.546
13.868
1.714
43.547
F
0.554
14.072
1.74
44.185
F 1/2
0.562
14.275
1.765
44.823
G
0.57
14.478
1.79
45.461
G 1/2
0.578
14.681
1.815
46.099
H
0.586
14.884
1.84
46.737
H 1/2
0.594
15.088
1.865
47.375
I
0.602
15.291
1.89
48.013
J
0.61
15.494
1.915
48.651
J 1/2
0.618
15.697
1.941
49.289
K
0.626
15.9
1.966
49.927
K 1/2
0.634
16.104
1.991
50.565
L
0.642
16.307
2.016
51.203
L 1/2
0.65
16.51
2.041
51.841
M
0.658
16.713
2.066
52.479
M 1/2
0.666
16.916
2.091
53.117
N
0.674
17.12
2.116
53.756
N 1/2
0.682
17.323
2.141
54.394
O
0.69
17.526
2.167
55.032
O 1/2
0.698
17.729
2.192
55.67
P
0.706
17.932
2.217
56.308
P 1/2
0.714
18.136
2.242
56.946
Q
0.722
18.339
2.267
57.584
Q 1/2
0.73
18.542
2.292
58.222
R
0.738
18.745
2.317
58.86
R 1/2
0.746
18.948
2.342
59.498
S
0.754
19.152
2.368
60.136
S 1/2
0.762
19.355
2.393
60.774
T
0.77
19.558
2.418
61.412
T 1/2
0.778
19.761
2.443
62.05
U
0.786
19.964
2.468
62.688
U 1/2
0.794
20.168
2.493
63.326
V
0.802
20.371
2.518
63.964
V 1/2
0.81
20.574
2.543
64.602
W
0.818
20.777
2.569
65.24
W 1/2
0.826
20.98
2.594
65.878
X
0.834
21.184
2.619
66.517
X 1/2
0.842
21.387
2.644
67.155
Y
0.85
21.59
2.669
67.793
Z
0.858
21.793
2.694
68.431
Z 1/2
0.866
21.996
2.719
69.069
0.874
22.2
2.744
69.707
Z1
0.882
22.403
2.769
70.345
0.89
22.606
2.795
70.983
Z2
0.898
22.809
2.82
71.621
Z3
0.906
23.012
2.845
72.259
0.914
23.216
2.87
72.897
Z4
0.922
23.419
2.895
73.535
0.93
23.622
2.92
74.173
0.938
23.825
2.945
74.811
0.946
24.028
2.97
75.449
0.954
24.232
2.996
76.087
0.962
24.435
3.021
76.725
0.97
24.638
3.046
77.363

Free Printable Ring Sizer

There are two ways to measure your ring size:

Ring Sizer, put it around your finger to measure your  ring size

1 – Printable Ring sizer

In order to print out this free online ring sizer above, be sure that your printer is set to 100%. In other words, make sure that you have not reduced the print size in ‘page set up.’ You can verify that the printable ring sizer printed correctly by measuring the ring sizer with a ruler; it should measure from left to right: 3 1/2 inches.

Once you have printed the free ring sizer, follow these directions to find your ring size:

Wrap a piece of loose string around your finger. Be sure to allow for the size of your knuckle.

With a pen, mark the point on the string where the end meets.

Using the chart, place the end of the string on the left hand border next to the word, ‘Son,’ and stretch along the sizer toward the numbers.

The pen mark will indicate your ring size.

2- Ring Measurement with a paper strip

To measure your ring size online you need the following equipment ( paper ring sizer):

  • scissors
  • ruler preferable in millimeters
  • sheet of paper
  • pen
  • tape

To measure your finger make sure you are in a room at room temperature. Different temperature make your fingers thicker or thinner. Keep also in mind that there are days that your body hold more water then other days, which make your fingers swell a little. Also during the day there can be a difference in finger size. If you notice that you finger size varies slightly, make sure you take the measurement at the right time.

Take the sheet of paper and cut it to 3 cm by 10 cm. Take the strip of paper ring sizer and fold it so it becomes 1cm X 10 cm. Take the folded paper and pull it a few time over an edge of a table so it becomes more flexible

Now wrap the piece of paper around the base of your finger, on which you want to wear the ring. Mark with a pen where the paper end overlaps. Now take the piece of paper of your finger and cut it about 1 cm longer then where you marked the paper with the pen. Take the tape and make a ring out it. Try the paper ring on the same finger and see if it comes on and off easily.

If the ring fits correctly cut the ring in two and measure the length of the paper in millimeters. Use the following table to convert length to the American ring size.

This is also a man ring sizer.

Best way to measure your ring is to order a plastic ring sizer