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How to Measure a Pocket Watch?

To get the most precise pocket watch measurement, you will want to measure the movement’s lower plate below the dial. Since the dial often extends beyond the movement, it’s not an accurate way of measuring the size of your pocket watch, however, with a well-trained eye it might be close enough to guess.

Movement vs Case Size

It’s important to know that a pocket watch size has nothing to do with the outside case diameter. A pocket watch can have various case sizes depending on the style and design. The case diameter is good for knowing how big the pocket watch is overall, if it will fit in your vest or watch pocket for example, but it is not relevant to the chart above.

Common Pocket Watch Sizes

Pocket watches come in all different sizes, but the most common will be 18s, 16s and 12s for men, or 0s, 6s and 8s for ladies pocket watches. 10s or 12s can be considered unisex. Early on, railroad pocket watches were allowed to be 18s or 16s, but eventually were required to be 16s.

What Does the S Mean?

The S next to the number just means “Size”. For example 18 is the same as 18S, and also the same as 18-Size. This S is usually added to the number so that you know it’s a size number rather than a jewel count. Similarly, you may also see something like 7J for jewels. Some dealers and enthusiasts might type these sizes differently.

Pocket Watch Sizes

These measurements are not related to the size of the case or dial. This chart converts American pocket watch sizes from inches to millimeters. You will notice from the chart below that pocket watches are typically measured in 30ths of an inch, also known as the “Lancashire Gauge” adopted from England. Remember, the sizes below refer to the movement size.

Size Inches Millimeters
22s
1 27/30″ (1.9″)
48.26
20s 1 25/30″ (1.83″)
46.56
18s common 1 23/30″ (1.766″)
44.86
17s 1 22/30″ (1.733″)
44.02
16s common 1 21/30″ (1.700″)
43.18
14s
1 19/30″ (1.633″)
41.48
12s common 1 17/30″ (1.566″)
39.78
10s common 1 15/30″ (1.500″)
38.10
8s common 1 13/30″ (1.433″)
36.40
6s common 1 11/30″ (1.366″)
34.70
0s common 1 5/30″ (1.166″)
29.62
3/0s
1 3/30″ (1.100″)
27.94
8/0s
14/15″ (0.933″)
23.71
12/0s
4/5″ (0.800″)
20.32
18/0s
3/5″ (0.600″)
15.24

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Phylicia
Phylicia
8 years ago

Love this

Michelle
Michelle
8 years ago

Thanks for sharing this chart. It will be very helpful when shopping for junk watches for use in Steampunk jewelry and art.

Enda McLarnon
Enda McLarnon
7 years ago

Just a quick note to let you know that for some reason the table or picture isn’t showing up

trevor king
trevor king
6 years ago

what is,the.differense between size 6 and size 60

Keystoner
Keystoner
2 years ago
Reply to  trevor king

6 is 34.7mm and 60 would be over 100mm probably. Did you see 60? that doesn’t even exist.

Phil
Phil
6 years ago

Hi, I am confused. All the data I have researched including the table here informs me that according to the serial number, the Elgin 7 jewel pocket watch I have is a 1927 16s, yet when I measure the actual movement it has a size of 40.6 mm indicates it is a 13s size. Can someone please clarify what’d size the movement is that I have. Cheers. Phil

Keystoner
Keystoner
2 years ago
Reply to  Phil

You’re probably measuring it incorrectly. Most people make the mistake of measuring the movement side. Like these guys said at the top of the page you have to measure the dial side.

clocknut99
clocknut99
2 months ago
Reply to  Keystoner

“These guys” were not very clear, they should have said DIAL PLATE, not lower plate.

Trevor VA
Trevor VA
1 month ago
Reply to  clocknut99

Same thing lol

Kyle Sheridan
Kyle Sheridan
2 years ago

What is the S on some of the pocket watch sizes? Can someone please tell me? Is there a difference between 18 and 18S? Thank you!

Kyle Sheridan
Kyle Sheridan
2 years ago
Reply to  Kyle Sheridan

Nevermind, sorry I just saw the chart and didn’t bother reading the rest of the post. I understand now, thanks!

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Ralph
Ralph
8 months ago

Is it possible to determine a pocket watch size without removing the movement from the case and if so how?

Don
Don
8 months ago
Reply to  Ralph

You can try and guess based on the measurement across the movement, but to get a real size you need to measure across the dial plate on the front of the watch.

clocknut99
clocknut99
2 months ago

43 mm seems like an awfully small pocket to watch.

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