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Watches

Watch Sizes – Lignes, Lancashire? Oh My!

How big is my watch? 18 size? 16 size? How do I know?

Pocket watches are often described as 18-size, 16-size, or something like that. What does that mean exactly? Like any good imperial unit, it’s complicated.

Note: One important thing to remember is that watch size is based on the size of the movement, not the watch case. This can be deceiving, as watch cases vary a lot.

Most American watches are sized on the Lancashire scale. The Lancashire scale is based on a 0-sized watch being 1″, but to account for the “fall” – the the extra amount added to the bottom plate of the watch to keep the watch from falling out of the case – you need to add 5/30″, so a 0-sized watch on the Lancashire scale would be 1 5/30″, or 1.667″. Each step larger than this adds 1/30″, therefore a 12-size watch = 1″ + 5/30″ + 12/30″, or 1.567″ and an 18-size watch = 1″ + 5/30″ + 18/30″, or 1.767′.

The other common scale is the Swiss Ligne scale, with “Ligne” being pronounced “line”. This scale is much more reasonable – one “Ligne” = 2.256mm or 0.089″. There are 12 Ligne per French inch.

Check out the table below for an exhaustive comparison. Happy measuring!

Lignes (Swiss watches)Lancashire (American watches)MillimetersInches
3 3/426/08.4590.3330
49.0230.3552
4 1/425/09.5870.3774
4 1/224/010.1510.3996
4 3/410.7150.4219
523/011.2790.4441
5 1/422/011.8430.4663
5 1/212.4070.4885
5 3/421/012.9710.5107
620/013.5350.5329
6 1/414.0990.5551
6 1/219/014.6630.5773
6 3/418/015.2270.5995
715.7910.6217
7 1/417/016.3550.6439
7 1/216/016.9190.6661
7 3/417.4830.6883
815/018.0470.7105
8 1/414/018.6110.7327
8 1/219.1750.7549
8 3/413/019.7390.7771
912/020.3030.7993
9 1/420.8670.8215
9 1/211/021.4300.8437
9 3/410/021.9940.8659
109/022.5580.8881
10 1/423.1220.9103
10 1/28/023.6860.9325
10 3/424.2500.9547
117/024.8140.9769
11 1/46/025.3870.9995
11 1/225.9421.0213
11 3/45/026.5061.0435
124/027.0701.0657
12 1/23/028.1981.1102
12 3/42/028.7621.1324
13029.3261.1546
13 1/2130.4531.1989
14231.5811.2433
14 1/4332.0461.2617
14 3/4433.2731.3100
15533.8381.3322
15 1/2634.9551.3762
15 3/4735.5291.3988
1636.0931.4210
16 1/4836.6571.4432
16 1/2937.2211.4654
171038.3491.5098
17 1/41138.9131.5320
17 3/41240.0411.5764
181340.6051.5986
18 1/21441.7331.6430
18 3/41542.2971.6652
1942.8611.6874
19 1/41643.4251.7096
19 1/21743.9891.7319
201845.1171.7763
212147.3721.8650
222349.6281.9539
232651.8842.0427
242954.1402.1315
253256.3962.2203
263458.6522.3091
273760.9072.3979
284063.1632.4867
294365.4192.5756
304567.6752.6644

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