Men's Watches

What is a Caliber?

Sometimes, watchmakers will not use the word movement to describe the mechanism of the watch. Instead, they will use caliber. In the world of watches, caliber and movement refer to the same thing. Sometimes, watchmakers will describe the movement of watches as such, “Caliber ABC123“. An example as shown in the Seiko SNS611P1, which features a Caliber 4T53.



The word caliber is also commonly used in the world of guns. Yes. That’s right, In the world of guns, caliber refers to the diameter of the bullet or the internal diameter of the gun barrel. To illustrate, here is an exploded diagram of the Glock, which shows you the barrel.

The barrel is pointed out as number 2 on the exploded diagram. (Source: Unkonwn:)


Here is also another picture guide of the diameter of the bullet.



According to, “a 0.50 caliber round, for example, is 0.5 inches in diameter”. Of course, you can also refer the caliber in the metric unit as well whereby “The standard NATO round is 5.56mm and is referred to as such”. In this logic, the bigger the round (0.6, 0.7,0.8,0.9), the bigger the diameter of the bullet and its barrel diameter.





Now, let’s learn a little bit about the history of why caliber is used to define a watch. The word caliber, according to, “goes back through the French calibre all the way to the late Arabic qalib a mold for casting bullets.”



noun cal· i· ber | \ˈka-lə-bər,  British also kə-ˈlē-\


The caliber “ultimately has its origins in the ancient Greek kalapous which means a shoemaker’s last( the wooden model around which a shoe is constructed).”




Now that we know the definition of caliber and how it is used in firearms, how does it relate to watches? Let’s take every information that we have and put them together. This is where it starts to get exciting!!


If we think about it logically, the size of the bullet mold will determine the size of the bullet. Similarly, the size of the shoemaker’s last will determine the size of the shoes. Since caliber refers to the diameter of the bullet, therefore, the term caliber refers to the diameter of the watch.




Henry Sully, the English clockmaker was the man responsible for the marrying caliber and watches. According to www., “Sully used this term circa 1715 to denote the layout and dimensions of the different movement pillars, wheels, barrel, etc”.


“Since then, “calibre” has been used to indicate the shape of the movement, its bridges, the origin of the watch, its maker’s name, and etc.” Don’t worry if the terms like the barrel, wheel, and others seem alien to you. I promise to explore more about these terms in the future.


In the meantime, you just need to know that caliber refers to the movement itself.




If you managed to make it to here, even when I threw confusing terms to you, then pat yourself on the back, because you deserve it!! Congratulations!! You have level up in your knowledge of watches!! I have always said from the beginning, “As men, we have knowledge of our watch(es)”.



Knowing the word caliber is one step, but with continuous improvement and learning, we can definitely be masters of our watches. To celebrate, click here to download our free basic guide to watch buying, which will be useful for you. Therefore, please stay tuned to my website as I explore the Seiko SNS611P1.







Leave a Reply

Your email address will not be published. Required fields are marked *