Pocket Watch Database



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

E. Howard Size Chart

Early production at E. Howard & Co. was based on Edward Howard's sizing system rather than the Lancashire Gauge that was later adopted by the American watch industry. Howard's letter classification system was based on the letter "A" representing one inch in diameter. Each subsequent letter progressing through the English alphabet represented an incremented value of 1/16th of an inch. Due to these minor size differences, early watches produced at the E. Howard factory required special cases specifically sized using the Howard size guage.

Size Diameter (Millimeters) Diameter (Inches) Diameter (Inches, Fraction) Closest Standard Lancashire Size
A 25.400 mm 1.000 in 1 in
B 26.988 mm 1.063 in 11/16 in
C 28.575 mm 1.125 in 12/16 in
D 30.163 mm 1.188 in 13/16 in
E 31.750 mm 1.250 in 14/16 in
F 33.338 mm 1.313 in 15/16 in
G 34.925 mm 1.375 in 16/16 in > 6s (34.71mm)
H 36.513 mm 1.438 in 17/16 in
I 38.100 mm 1.500 in 18/16 in = 10 (38.10mm)
J 39.688 mm 1.563 in 19/16 in < 12 (39.79mm)
K 41.275 mm 1.625 in 110/16 in < 14 (41.49mm)
L 42.863 mm 1.688 in 111/16 in < 16 (43.18mm)
M 44.450 mm 1.750 in 112/16 in
N 46.038 mm 1.813 in 113/16 in > 18 (45.72mm)
O 47.625 mm 1.875 in 114/16 in
P 49.213 mm 1.938 in 115/16 in
Q 50.800 mm 2.000 in 2 in
R 52.388 mm 2.063 in 21/16 in
S 53.975 mm 2.125 in 22/16 in
T 55.563 mm 2.188 in 23/16 in
U 57.150 mm 2.250 in 24/16 in
V 58.738 mm 2.313 in 25/16 in
W 60.325 mm 2.375 in 26/16 in
X 61.913 mm 2.438 in 27/16 in
Y 63.500 mm 2.500 in 28/16 in
Z 65.088 mm 2.563 in 29/16 in