What Is 5atm Water Resistant In A Watch?

What does it mean when a watch is 5atm water resistant? Simply put, a watch that is 5atm water resistant, can withstand the equivalent to a depth of 50 meters, or 164 feet underwater. But there is much more to this story! Read on to find out more!

We previously did an article on the Wr20bar, which explains that 1 bar is equal to a depth of 33 feet underwater. So what about ATM then? What exactly does ATM stand for?

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What Is ATM In Water Resistance?

The term ATM, refers to “atmospheres”, which is the amount of pressure that a device can take. This is typically measured in meters. So the ATM water resistance of a watch would be the amount of meters of water pressure the watch can take.

So now you might wonder how to determine how many meters of water resistance you would get based on its ATM number. To determine the number of meters of water resistance of a watch based on its ATM number, you would simply multiply the ATM number by 10.

This is why a watch with 5atm water resistance has a water resistance of 50 meters. Because 5×10 is 50. The same would apply to a watch that has a water resistance of 3atm. That would be 30 meters, because 3×10 is 30. And a watch that is has a 10atm water resistance, would be water resistant 100 meters, and so on, and so on.

So then why exactly is ATM, or atmospheres measured this way? Why not just use the number of meters?

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Why Is ATM Water Resistance Measured The Way It Is?

So we know that you can find out what a watch’s water resistance is in meters from the ATM. It’s simply multiplying the ATM by 10. But there must be a legitimate reason as to why we even use ATM at all, instead of just the meters or feet.

Well the reason for this is that technically speaking, ATM is actually referring to the air pressure at sea level. This starting point at sea level would already be referred to as 1 ATM. This is the air pressure from earth’s atmosphere, hence the term “ATM”.

How ATM Is Calculated

I will try not to get to confusing here, but the 1ATM is equivalent to 1 bar. If you recall what I mentioned earlier when I stated that 1 bar equals a depth of 33 feet. Well 33 feet is the equivalent of 10 meters! So in atmospheres then, the starting point for atmospheric pressure at sea level is 10 meters. This is the difference between ATM measurements and just using straight meters and feet.

So now if you are still following, then our starting point for measuring ATM is at sea level. This equals 1ATM, or 10 meters. Now here’s where we go from there. Once you go below sea level, then for every 10 meters you go below sea level, there is 1 bar of water pressure added to the atmospheric pressure.

So technically speaking, 10 meters below sea level would be 2ATM, 20 meters would be 3ATM, 30 meters would be 4ATM, and so on. But wait! Why then would a watch rated 5ATM be listed as having a water resistance of 50 meters. Shouldn’t it be 40 meters?

Well, in this case, 5ATM should mean 40 meters below sea level. But in the case of water resistance for watches, it means 50 meters. This is probably done to simplify things for consumers.

Ok, so that was quite the longwinded explanation! There is one more part I will talk about though. And that is what this means in reference to how water resistant a watch actually is. For instance, can a watch that has a water resistance rating of 5atm, really withstand a a depth of 50 meters underwater. Well sort of, but not really……

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What 5atm Water Resistant In A Watch Really Means

This is the part where I will talk about what the ATM really means in terms of actual real world water resistance.

Using 5atm as an example, if a watch has a water resistance rating of 5atm, this means that it can withstand a water pressure equivalent to a depth of 50 meters. What this means is that a watch has been tested by being sprayed with water at a force equivalent to the pressure 50 meters.

So in theory, a watch rated 5atm could withstand a depth of 50 meters, but it probably wouldn’t. This is because the test just shows that it can withstand that pressure for a brief moment at the least. To actually dive to 50 meters would mean that it is being exposed to continuous, increasing pressure. This is something that the watch probably cannot withstand.

If we are going to be accurate with real world applications, then this means that anything below 10atm shouldn’t be worn in the water to play it safe. There are actually some general guidelines that you can follow in regards to a watch’s ATM rating.

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ATM General Guidelines

By sticking to these general rules of thumb, you can ensure you do not damage your watch by submerging it in water at a depth beyond what it can handle.

• 3-5 ATM: Can withstand splashes of water, rain, and maybe even showering, but shouldn’t be fully submerged in water.
• 10 ATM: Can handle swimming, snorkeling, and maybe even scuba diving.
• 20 ATM: Can handle deep diving.
• 30 ATM and up: Suitable for professional diving, or saturation diving.

Also note that even a watch with an ATM rating of 10, could be considered a diving watch, assuming it meets the ISO certification requirements for water resistance. Regardless of a watch’s listed ATM rating, it is always a good idea to check if it meets any official certified standards for water resistance.

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Conclusion

For the sake of keeping this article short, I think that this is a good place to wrap things up. Now you know what 5atm water resistant is in a watch and more. I hope that I’ve explained things in a way that makes sense. Sometimes the details can be a bit confusing.

If you enjoyed learning about this topic, we cover various different topics pertaining to watches in our Info Section. Feel free to check that out when you have the time, and thanks for reading!