# What does 100 meter (10 ATM) waterproof mean and who came up with this sh*t?

Everyone who has never dealt with watches or Smartwatches in detail knows the problem: you see a watch, read “30 meters waterproof” and think you could dive up to 30 meters with it. But it’s not true!

## Now what does 100 meters waterproof mean?

The water tightness test generates a pressure that corresponds to the pressure at a depth of 100 meters. However only static pressure without any movement. The watch must withstand this pressure for a certain period of time. However, much higher dynamic pressure is generated when moving in water or through a showerhead. The rules for this pressure test are regulated in the international ISO 22810:2010 or the German DIN 8310 standard. However, this test does not define real swimming or diving depths, so the following classification has become common practice:

### suitable for

30 meters 3 Bar washing hands / splash water
50 meters 5 Bar bath / shower
100 meters 10 Bar swimming / snorkeling
200+ meters 20+ Bar diving

## 10 ATM? 10 bar? 100 meters waterproof? What’s the connection?

“ATM” stands for “physical atmosphere” and is a unit of pressure that was previously in use. In the watch trade, it has held its own until today. Since it cannot be exact by definition (for more information see Wikipedia) it was replaced by the unit “bar” in 1978 in Germany and Austria. 1 bar corresponds approximately to the air pressure on the earth’s surface or a water column of 10 meters height. 10 ATM corresponds to approximately 10 bar, which is approximately the pressure that prevails at a depth of 100 meters. This is where the term “100 meters waterproof” comes from.

## Why is there no generally understandable classification?

As described above, the ISO 22810:2010 standard only regulates the static pressure that a watch must withstand. In real life, however, this information is quite worthless. For example, if you jump flat from the edge of the pool into the water, the watch must withstand much higher pressure than if you let it glide gently to the ground in the pool. In the first example, the watch may only be exposed to 30 cm water depth, in the second 1.50 meters. Nevertheless, the risk of water ingress is much greater in the first example due to the higher dynamic pressure.