What is ATM Water Resistance

One of the most important features to consider when investing in a watch is the ATM rating. Normally, watches have a water protection mechanism that helps prevent water from reaching the delicate parts housed in the body with the level of water resistance varying from gadget to gadget.

And the unit for measuring such ratings is popularly known as ATM water resistance. ATM is a sobriquet and an abbreviation of atmospheres with one such unit being the equivalent of the pressure at sea level. Therefore a reading of 9 ATM, or sometimes 9 bars, simply means the watch is capable of withstanding nine times the pressure at sea level without incurring water damage.

Every single watch comes with a resistance rating spelled out clearly somewhere on the case back or dial but for a long time people have often misinterpreted these figures and thereby end up losing their watches to water damage when they thought they should be immune to it. For instance, let’s take the case of a 20 meter ATM rating. Usually, this resistance is referenced to a stationary point which means it doesn’t take into account motions at that depth so it might not be a good idea to go swimming at the rated ATM depth as this could break the seal since movement generates increased pressure.

Summary Table of ATM Ratings for Minimalist Watches

For those who want the cliff notes version —

ATM RatingWhat it meansWhich watch qualifies
0 ATMNo water allowed!"Splash Proof" OG Watch
3 ATMCan survive showers.MVMT Boulevard
5 ATMCan dive into pool.Original Grain Wooden Watch
10 ATMCan go snorkeling.Vincero Kairos
20 ATMLet's find the Titanic!High End Chronograph Watches

What are the different levels of ATM ratings?

Each rating obviously alludes to a different level of water resistance tailored to suit various purposes. To shed more light on the matter, let’s break down some sample ATM water resistance ratings (as supported by the ISO):

0 ATM/bar

Well, if you time telling companion reads 0 on the ATM scale, then it’s probably not a good idea to let it anywhere near water as it is barely water resistance. The water protection usually entails basic seal mechanisms and not much else, therefore, it is best to take off such a watch before coming into contact with water e.g. when washing your hands. The rating corresponds to O meters below sea level which loosely translates to very little tolerance to water.

3 ATM/bar

The difference, in essence, all boils down to the level of sealing and in this case, this rating means the watch should handle depths pressure of up to about 30 meters. However, it is not submersible as most people would have you wrongly believe. Such watches can take a splashing like in drizzling rain or whilst washing hands but it should never be worn in the shower or any such scenarios where it is likely to be immersed in water. Normally, luxury watches fall into these two highlighted categories (0 and 3 bar) as the weight of seals and reinforcements are sacrificed for aesthetic finesse.

5 ATM/bar

Akin to 50 meters below sea level, a 5 ATM spec. is the standard definition of water resistance and is perfect for diving into the pool, swimming, showering, walking in the snow or rain and even fishing as it can endure water immersion for fairly long periods of times. However, high-speed water sports and scuba diving is where a 5 bar watch draws the line.

10 ATM/bar

The resistance only gets better higher up the scale as is evident by now with the 10 bar (100 meters below sea level) proving a step up from its predecessor. It is built for taking to the waves i.e. surfing, snorkeling and is your best bet at a good swimming companion. In a nutshell, such a rating basically means that the watch thrives in almost every sort of elevated water resistance.

20 ATM/bar

Often touted as the diver’s setting, the 20 bar (200 meters) is tailored specifically for skin diving and high-speed sporting. Usually, the rating is 125 % above the specified rating as the manufacturer also takes into consideration the added pressure resulting from movements by the diver that in turn increases the turbulence acting on the watch. 20 ATM watches are also meant for professional marine activity with the watch often embedded with a “Diver” tag so as to specifically outline its purpose. However, for mixed gas or deep sea diving, it is of the essence you get the go-ahead of a professional before use.

There you have it, some of the most standard watch ratings broken down in plain English. Also, keep in mind that a watch’s water resistance prowess depreciates with age so a 1950’s 10 bar watch, for instance, might not be as resistant as a new millennium model of the same spec. Take the ATM rating into consideration next time you shopping for a new watch so as to understand exactly what you’re getting and if it is the right fit for you.

Informative Video on ATM Ratings