Watch movement size conversion chart
There are three major ways in which watch movements are measured Ligne, mm, and American.
1 ligne = 2.256 mm.
American movement sizes to Ligne to mm conversion
Size Ligne mm
18/0 6 3/4 15.25
17/0 1 1/8 16.08
16/0 7 1/2 16.92
15/0 7 7/8 17.78
14/0 8 1/4 18.62
13/0 8 5/8 19.46
12/0 9 1/8 20.32
11/0 9 3/8 21.16
10/0 9 3/4 22.00
9/0 10 1/8 22.86
8/0 10 1/2 23.70
7/0 10 7/8 24.54
6/0 11 1/4 25.40
5/0 11 5/8 26.24
4/0 12 1/8 27.08
3/0 12 3/8 27.94
2/0 12 3/4 28.78
0 13 1/8 29.62
1 13 1/2 30.48
2 13 7/8 31.32
3 14 1/4 32.16
4 14 7/8 33.02
5 15 1/8 33.86
6 15 3/8 34.70
7 15 3/4 35.56
8 16 1/8 36.40
9 16 1/2 37.24
10 16 7/8 38.10
11 17 1/4 38.94
12 17 5/8 39.78
13 18 1/8 40.64
14 18 3/8 41.48
15 18 3/4 42.32
16 19 1/8 43.18
17 19 1/2 44.02
18 19 7/8 44.86
19 20 1/4 45.72
20 20 3/4 46.56
Swiss movement sizes, Ligne to mm conversion
Lignes mm
7 15.79
8 18.05
9 20.30
10 22.56
11 24.81
12 27.07
13 29.32
14 31.58
15 33.84
16 36.09
17 38.35
18 40.60
19 42.86
20 45.11
21 47.37
22 49.63
Common American movement sizes
26/0, 22/0, 21/0, 20/0, 18/0, 16/0, 15/0, 14/0, 12/0, 10/0, 8/0, 6/0, 5/0, 4/0, 3/0, 0, 6,, 8, 10, 12, 14, 16, 18
Common Swiss movement sizes ( * sizes are most common )
Lignes mm
3 3/4 x 6 3/4 9.0 x 15.15
3 3/4 x 8 1/4 9.0 x 19.4
3 3/4 x 10 9.0 x 21.0
*5 1/2 x 6 3/4 13.0 x 15.15
*6 3/4 x 8 15.3 x 17.8
*7 3/4 17.2
8 1/4 18.2
*8 3/4 19.4
*10 1/2 23.3
*11 1/2 25.6
12 1/2 28.4
16 1/2 36.6