What Size Is My Watch?

When a collector refers to an American pocket watch's "size," he or she is generally referring to the diameter of the watch movement only, not the case. The same size watch movement will usually fit in a variety of different size cases, so the size of the case is usually not helpful in identifying the watch. European watches are typically referred to by their size in millimeters. A small ladies' watch might be 30 or 35mm, whereas a men's watch could be upwards of 50 or 60mm. American watches, on the other hand, have their own special sizing scale. Most American watches fall between 0 and 18 size, with 0 being the smallest and 18 being the largest. The most common sizes are 18, 16 and 12 for men's watches, and 8, 6 and 0 for ladies' watches. The size 10 watch is right in the middle and is generally considered to be either a men's or a ladies' watch. The following table shows the standard American watch movement sizes and their equivalent size in inches:

Watch Size Size in Inches
18 1 23/30 [1.8]
16 1 21/30 [1.7]
12 1 17/30 [1.566]
10 1 [1.5]
8 1 13/30 [1.433]
6 1 11/30 [1.366]
0 1 5/30 [1.166]

As you might expect, it can be a bit tricky measuring a watch movement to determine its size, not only because many of the sizes are so close to each other, but also because it's not that easy to measure such odd sizes in the first place. Also, the sizing chart above refers to the size of the plate under the dial [which may or may not be the same diameter as the dial itself], and on some watches that plate has a slightly different diameter than the plate visible when simply viewing the movement. Experienced collectors, however, can often tell the size of most watches simply by looking at the movement and comparing it to other, similar, watches they have seen before. As with any skill, this ability comes primarily through experience, but here are some quick pointers when dealing with American watches:

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All text © 2000-2002 Barry S. Goldberg, Esq.

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