Understanding ATM in Horology

ATM, short for Atmospheres, is a unit of pressure. In the context of watches, it refers to the level of water resistance a watch has. It’s a standard measure used across the watchmaking industry, and it’s crucial for determining how and where a watch can be used.

One ATM is equivalent to the pressure exerted by 10 meters of water at sea level. Thus, a watch with a water resistance of 5 ATM can theoretically withstand the pressure at a depth of 50 meters underwater. However, this doesn’t mean that the watch can be used for diving to such depths. There are other factors to consider, which we will explore later in this article.

The Importance of ATM in Luxury Mechanical Watches

Luxury mechanical watches are not just timekeeping devices but pieces of art. They are meticulously crafted with precision and care. However, they are also meant to be worn, and that means they must withstand the elements, including water. The ATM rating of a watch gives you an idea of how much water pressure the watch can withstand.

For a luxury mechanical watch, a higher ATM rating is often desirable. It indicates a higher level of craftsmanship and quality, as it requires precision and expertise to create a watch that can withstand higher pressures. Furthermore, a higher ATM rating also expands the situations in which the watch can be worn, enhancing its versatility.

ATM Ratings and Their Meanings

ATM ratings on watches can range from 1 ATM, which offers minimal water resistance, to 100 ATM, which is suitable for deep-sea diving. However, these ratings can be misleading if not understood correctly. Here’s a breakdown of what different ATM ratings mean in practical terms.

A watch with a rating of 1 ATM (10 meters) is resistant to minor splashes of water. However, it should not be submerged. A rating of 3 ATM (30 meters) means the watch can withstand brief immersions, such as accidentally dropping it in the sink, but it’s not suitable for swimming. A 5 ATM (50 meters) watch can be worn for swimming in shallow water.

ATM Ratings for Diving Watches

For diving watches, the ATM rating needs to be significantly higher. A watch with a 10 ATM (100 meters) rating is suitable for snorkeling, while a 20 ATM (200 meters) watch can be used for high-impact water sports and professional marine activity. Watches with a rating of 30 ATM (300 meters) or higher are suitable for professional diving.

However, it’s important to note that these are theoretical values. In reality, the water resistance of a watch can be affected by factors such as temperature changes, the age of the watch, and the condition of its seals. Therefore, it’s always a good idea to err on the side of caution when using your watch in water.

How ATM is Tested in Luxury Mechanical Watches

Testing the ATM rating of a luxury mechanical watch is a complex process that requires specialized equipment. The watch is placed in a pressurized chamber filled with air. The pressure is then gradually increased to the desired ATM rating. If the watch case expands by more than a certain amount, it indicates that air has leaked into the watch, and it fails the test.

After the air pressure test, the watch undergoes a water pressure test. It’s submerged in water and subjected to the pressure corresponding to its ATM rating. The watch is then carefully inspected for any signs of water intrusion. If it passes both tests, it’s deemed to have the stated ATM rating.

The Role of Watch Seals in ATM

The seals, or gaskets, of a watch play a crucial role in its water resistance. They prevent water from entering the watch case, protecting the delicate mechanical movement inside. The quality and condition of these seals significantly affect the ATM rating of a watch.

Over time, the seals of a watch can degrade, reducing its water resistance. Therefore, it’s recommended to have the seals of a luxury mechanical watch checked and replaced regularly, especially if the watch is frequently used in water. This will ensure that the watch maintains its stated ATM rating and continues to function optimally.

ATM in the Context of Swiss-Made Luxury Mechanical Watches

Swiss-made luxury mechanical watches are renowned for their superior craftsmanship and precision. These watches often come with high ATM ratings, reflecting their quality and durability. Brands like Rolex, Omega, and Breitling offer watches with ATM ratings of up to 100, suitable for deep-sea diving.

However, a high ATM rating is not the only factor that makes these watches exceptional. They also feature advanced sealing technologies, high-quality materials, and meticulous assembly processes, all of which contribute to their water resistance. Thus, when you buy a Swiss-made luxury mechanical watch, you’re not just buying a timepiece, but a testament to exceptional craftsmanship and engineering.

ATM and the Luxury of Swiss-Made Watches

The ATM rating of a Swiss-made luxury mechanical watch is not just a technical specification. It’s a symbol of the watch’s quality, durability, and the skill of its makers. A high ATM rating indicates that the watch has been crafted with utmost precision and care, capable of withstanding harsh conditions while maintaining its elegance and functionality.

Moreover, a high ATM rating also adds to the versatility of the watch. It allows the wearer to use the watch in a variety of settings, from formal events to adventurous underwater expeditions. This versatility is a key aspect of the luxury that Swiss-made watches offer.


Understanding ATM in the context of luxury mechanical watches is not just about knowing how deep you can dive with your watch. It’s about appreciating the craftsmanship, precision, and engineering that goes into creating a watch that can withstand the pressure of the deep sea while keeping time with impeccable accuracy.

So, the next time you come across the term ATM while exploring the world of luxury mechanical watches, remember that it’s not just a number. It’s a testament to the watch’s resilience, a symbol of its quality, and a reflection of the skill and passion of the watchmakers who crafted it.


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