Pocket Watch Database

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Pocket Watch Size Chart

Use the size chart below to determine the size of your watch by carefully measuring the pillar plate (dial side) diameter of the movement with a micrometer.

The sizing system utilized by American watch companies is derived from the Lancashire Gauge, popularized in the English watchmaking trade. One inch is taken as a basing figure and 5/30 of an inch is added for the fall or drop of the dial, resulting in 1 5/30 of an inch referred to as "naught size” (0s). Subsequently, the addition or subtraction of each 1/30” increment results in scaling the size up or down. For example, size 12 measures 1 17/30” (12 increments of 1/30” from the naught size of 1 5/30”).

Note: Companies did not strictly adhere to this sizing standard, using a 6/30" drop instead of the 5/30" for larger movements. As a result, “18 Size” American movements are actually 19 Size according to the Lancashire Gauge system.


= Standard Size Utilized by American Companies
Size Diameter (Millimeters) Diameter (Inches) Diameter (Inches, Fraction)
21/0s 12.70 mm 0.500 in 1/2 in
20/0s 13.55 mm 0.533 in 8/15 in
19/0s 14.39 mm 0.567 in 17/30 in
18/0s 15.24 mm 0.600 in 3/5 in
17/0s 16.09 mm 0.633 in 19/30 in
16/0s 16.93 mm 0.667 in 2/3 in
15/0s 17.78 mm 0.700 in 7/10 in
14/0s 18.63 mm 0.733 in 11/15 in
13/0s 19.47 mm 0.767 in 23/30 in
12/0s 20.32 mm 0.800 in 4/5 in
11/0s 21.17 mm 0.833 in 5/6 in
10/0s 22.01 mm 0.867 in 13/15 in
9/0s 22.86 mm 0.900 in 9/10 in
8/0s 23.71 mm 0.933 in 14/15 in
7/0s 24.55 mm 0.967 in 29/30 in
6/0s 25.40 mm 1.000 in 1 in
5/0s 26.25 mm 1.033 in 1 1/30 in
4/0s 27.09 mm 1.067 in 1 1/15 in
3/0s 27.94 mm 1.100 in 1 1/10 in
2/0s 28.79 mm 1.133 in 1 2/15 in
0s 29.63 mm 1.167 in 1 1/6 in
1s 30.48 mm 1.200 in 1 1/5 in
2s 31.33 mm 1.233 in 1 7/30 in
3s 32.17 mm 1.267 in 1 4/15 in
4s 33.02 mm 1.300 in 1 3/10 in
5s 33.87 mm 1.333 in 1 1/3 in
6s 34.71 mm 1.367 in 1 11/30 in
7s 35.56 mm 1.400 in 1 2/5 in
8s 36.41 mm 1.433 in 1 13/30 in
9s 37.25 mm 1.467 in 1 7/15 in
10s 38.10 mm 1.500 in 1 1/2 in
11s 38.95 mm 1.533 in 1 8/15 in
12s 39.79 mm 1.567 in 1 17/30 in
13s 40.64 mm 1.600 in 1 3/5 in
14s 41.49 mm 1.633 in 1 19/30 in
15s 42.33 mm 1.667 in 1 2/3 in
16s 43.18 mm 1.700 in 1 7/10 in
17s 44.03 mm 1.733 in 1 11/15 in
18s 44.87 mm 1.767 in 1 23/30 in
Note: American 18s Movements Measure 1.800" Due to the Increased 6/30" Drop.
19s 45.72 mm 1.800 in 1 4/5 in
20s 46.57 mm 1.833 in 1 5/6 in
21s 47.41 mm 1.867 in 1 13/15 in
22s 48.26 mm 1.900 in 1 9/10 in
23s 49.11 mm 1.933 in 1 14/15 in
24s 49.95 mm 1.967 in 1 29/30 in
25s 50.80 mm 2.000 in 2 in
26s 51.65 mm 2.033 in 2 1/30 in
27s 52.49 mm 2.067 in 2 1/15 in
28s 53.34 mm 2.100 in 2 1/10 in
29s 54.19 mm 2.133 in 2 2/15 in
30s 55.03 mm 2.167 in 2 1/6 in
31s 55.88 mm 2.200 in 2 1/5 in
32s 56.73 mm 2.233 in 2 7/30 in
33s 57.57 mm 2.267 in 2 4/15 in
34s 58.42 mm 2.300 in 2 3/10 in
35s 59.27 mm 2.333 in 2 1/3 in
36s 60.11 mm 2.367 in 2 11/30 in