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Watch Sizes

There are a number of different systems of measuring the size of a watch. Which system you should use depends on who made the watch and who you are talking to. In all the systems, the greater the number, the larger the watch.

Elgin almost always used the Lancashire gauge, so it will be described in the most detail.

Types of Watch Size Systems

Lancashire gauge
This is a bizarre system that was used by most American watch companies and for many European watches that were imported into America. Most pocket watch are described using this system.

Examples:   18s   16s   10/0s

Metric   (millimeters)
This system is used by most modern watch companies to describe their watches. Sometimes you will see it used to describe older watches where the manufacture originally used a different system, but this can lead to confusion.

Examples:   44.1mm   34mm

This was the system used by most Swiss and French watch companies before they switched to the Metric system. It comes from the measurement system that the French used before they invented the Metric system in the late 1700s. Why it was still used into the late 1900s for watches is anyones guess. Many wrist watches are described using this system, although millimeters are also frequently used.

Examples:   17L   11¼L

Dennison gauge
This is a system used by the E. Howard Watch Company and it was rarely used by other companies. Just to make life harder, it uses letter designations instead of numbers. (Dennison was one of the founders of the E. Howard company.)

Examples:   N   L

Which System To Use?

Considering all the different systems and the quirkiness of them, you may wonder which one is "best" or which you should use. The short answer is that watch companies advertised watches as being a certain size, and collectors generally call those watches by whatever size the watch company used. If you know exactly what you are doing, you can usually measure the watch and come up with the same number as the watch company, but not always. It helps a little bit that American watch companies generally used only even numbered Lancashire gauge sizes. The fact that most places don't even get the size in inches of an 18s watch correct (see below) tells you how rarely watches are actually measured.

Popular Watch Sizes Changed Over Time

Over the years, the sizes of watches have tended to shrink, so what would be considered a small "woman's sized" watch in the 1850s would be about the same diameter of a "man's sized" pocket watch in the 1920s. Men's pocket watches started out at 18s or even 20s in the mid-1800s. By around 1910, the most common size had dropped to a 16s and by the 1920s, it had dropped to a 12s. Women's pocket watches started at 10s, then 6s and then 0s. The smaller of these watches would often be worn as pendant watches that were hung on a chain from the neck or attached to a broach. Watches reached their minimum size in 1940s and 1950s and have gradually been getting larger since then. After 200 years of shrinking watches, consumers stopped automatically associating "smaller" with being "more modern" and "higher quality." (See the "Wedding Ring Test" Elgin advertisement for an extreme example of how small watches became.)

The Lancashire Gauge   (Used by Elgin)

The Lancashire gauge is one of the most common systems for measuring watch sizes, and in many circles, it is used almost exclusively. It is the system that Elgin used, and it is what is used on the rest of this web site. Too bad it is such a strange system.

One of the first strange things that you will notice about this system is the vast majority of explanations of the Lancashire gauge, along with the gauges and tables that claim to measure it, are wrong! They fail to take into account the change in the amount of "fall" for sizes over 16s. It should be remembered that most of these explanations, tables and gauges were made after 1920, while most 17s, 18s and 20s watches were made well before then.

The Lancashire gauge is based on the 0s being 1 inch in diameter, but an additional 5/30" was added for the "fall", except when the size is over 16s, in which case 6/30" was added for the "fall", except when the larger watch was designed after around 1910 in which case only 5/30" fall was added. The "fall" is the amount added to the dial plate (aka bottom plate) to form a flange to keep the watch from falling out of the case.

So, a 0s watch would be 1" + 5/30" = 1.1667". Each step larger adds an additional 1/30 of an inch. Why 1/30" instead of 1/32" or something? I have no idea. As I've said, watch sizes are crazy. A 6s watch would be 1" + 5/30" + 6/30" = 1 11/30" = 1.3667" and an 18s watch would be 1" + 6/30" + 18/30" = 1.8".

Everything clear so far? Ok, well, there are actually a few more exceptions to the Lancashire gauge, or at least how watch companies sometimes used them. Sometimes the watch companies would use an oversized dial and call the watch a different size. Sometimes watch companies would list the same watch as being two different sizes depending on which catalog you looked at.

Once watches got smaller than 0s, they first used the notation of "00s" and "000s", but that quickly became awkward, so they changed to using "2/0s" and "3/0s" instead. This is why you will never see a watch size of 1/0s, and why a 3/0s watch is only 2 sizes smaller than a 0s watch. Wrist watches tend to range from 6s down to 26/0s for the smallest lady's wrist watches.

More information on the quirks of the Lancashire gauge can be found in the NAWCC bulletin #177 page 298 from August 1975 in an article written by W. L. Pritchard.

The Metric System

Modern watches are just measured in millimeters. This is the easiest and most logical system for measuring watches. Too bad most of the old documents don't use it. Old watch sizes converted into millimeters come up with odd numbers and using mm instead of what was used in the original documentation can cause confusion.

The Ligne System

The Swiss used a different system based on the "Ligne" (which is French for "line" and pronounced "line"). One Ligne is 2.2558291mm or 0.088812168 inches. Like the Lancashire gauge, this is an old system but it makes a little more sense than the Lancashire gauge. There are 12 Ligne to one French inch (pouce, French for thumb) and 12 pouce to a French foot (pied).

The Dennison Gauge

Aaron Dennison was one of the "Fathers" of the American watch industry, and as such, he invented several standards of measuring watches and mainsprings. The Dennison Gauge for watch sizes is based on a size A being 1" and for each additional size larger, you would add 1/16". The most common sizes were N (1 11/16), which is close to 18s and L (1 10/16), which is close to 16s.

What Exactly Is Being Measured?

The measurement to determine the size is supposed to be through the widest part of the narrowest diameter. If the watch movement is round, then you should measure across whichever plates are the widest, whether the plates are on the top or the bottom or in the middle. If the movement is rectangular, barrel shaped, or oval, you still have to measure across whichever plates are widest, but you have to use the narrow cross section which still goes through the center of the watch. So, if you extend the length of a rectangular movement, you won't change the size. If, instead, you change the width, you will change the watch size. Did I mention that watch sizes are strange?

Table of Watch Sizes

This table can be used to convert a watch size from one system into another. Numbers that are in bold are exact, as are the inches and millimeters columns.

Inches Lanca-
Ligne Denn-
4.000085s 101.60045 
2.400037s 60.96027 
1.933323s 49.10721¾P
1.900022s 48.260  
1.875020s 47.625 O
1.866720s 47.41321O
1.842919s 46.80820¾ 
1.833319s 46.567  
1.8206 46.24420½N
1.8125 46.03720½N
1.800018s 45.72020¼N
1.776217s 45.11720 
1.766717s 44.873  
1.7540 44.55319¾M
1.7500 44.45019¾M
1.731816s 43.98919½ 
1.709616s 43.42519¼ 
1.700016s 43.180 L
1.6875 42.86219L
1.666715s 42.33318¾ 
1.643014s 41.73318½ 
1.633314s 41.487 K
1.625014s 41.27518¼K
1.6208 41.16918¼K
1.600013s 40.64018 
1.576412s 40.04117¾ 
1.566712s 39.793 J
1.562512s 39.68817½J
1.5542 39.47717½J
1.533311s 38.94717¼ 
1.509810s 38.34917I
1.500010s 38.100 I
1.4876 37.78516¾I
1.4667 9s 37.25316½ 
1.4432 8s 36.65716¼H
1.4375 8s 36.51216¼H
1.4333 8s 36.407 H
1.4210 36.09316 
1.4000 7s 35.56015¾ 
1.3766 6s 34.96515½G
1.3667 6s 34.713 G
1.3544 34.40115¼ 
1.3333 5s 33.86715 
1.3125 33.33714¾F
1.3000 4s 33.020 F
1.2878 32.71014½ 
1.2667 3s 32.17314¼ 
1.2500 31.75014E
1.2434 31.58214E
1.2333 2s 31.327  
1.2212 31.01813¾ 
1.2000 1s 30.48013½D
1.1875 30.162 D
1.1768 29.89013¼D
Inches Lanca-
Ligne Denn-
1.1667 0s 29.633  
1.1546 29.32613 
1.1333 2/0s28.78712¾C
1.1250 2/0s28.57512¾C
1.1102 28.19812½ 
1.1000 3/0s27.940  
1.0879 27.63412¼ 
1.0667 4/0s27.09312B
1.0625 4/0s26.98712B
1.0435 26.50611¾ 
1.0333 5/0s26.247  
1.0213 25.94211½ 
1.0000 6/0s25.40011¼A
0.9769 24.81411 
0.9667 7/0s24.553  
0.9547 24.25010¾ 
0.9333 8/0s23.70710½ 
0.9103 23.12210¼ 
0.9000 9/0s22.860  
0.8881 22.55810 
0.8437 21.430 
0.8215 20.866 
0.800012/0s20.320 9 
0.7771 19.739 
0.7549 19.175 
0.7105 18.047 8 
0.6883 17.483 
0.6439 16.355 
0.6217 15.791 7 
0.5773 14.663 
0.5551 14.099 
0.533320/0s13.547 6 
0.5107 12.971 
0.4885 12.407 
0.4441 11.279 5 
0.4219 10.715 
0.3775  9.587 
0.366725/0s 9.313  
0.3552  9.023 4 
0.333326/0s 8.467 
0.3108  7.895 

While I'm not an expert, I believe the information on this page is correct. Please send suggestions and corrections to the webmaster.
This web site runs on 100% Open Source Software. This web page was last changed on 10/04/2002 at 00:41:29.