If you’re looking to buy a new smartwatch, fitness tracker or another wearable, you’ve probably come across the term ‘ATM’ as a way of expressing water resistance.
Here’s everything you need to know about ATM, including what each number means and how it differs from an IP rating.
What is ATM water resistance?
ATM is a water resistance measurement commonly featured on both smartwatches and traditional watches.
The term ‘ATM’ is an abbreviated version of the word ‘atmosphere’ and is used to describe the amount of pressure a device can withstand underwater.
The specific amount of pressure a device can handle is typically determined in laboratory conditions, with numbers like 1 ATM, 3 ATM and 5 ATM used to convey exactly how water resistant it is. Generally speaking, 10m of depth is equal to 1 atmosphere of pressure (or ATM). The higher the number, the more pressure the product can withstand underwater.
The definitions and test conditions for each ATM classification are officially determined by the International Organisation for Standardisation in ISO 22810.
You can see Samsung’s summary of the classifications below:
What is the difference between ATM and an IP rating?
If you’ve ever looked into the water resistance of a smartphone or pair of earbuds, you may be familiar with the term ‘IP’. Plenty of flagship phones carry an IP rating of IP68 these days, for example.
So, what is the difference between IP and ATM?
Like ATM, an IP rating is a way of classifying exactly how water resistant a device is. IP stands for Ingress Protection.
An IP rating is divided into two numbers – the first refers to how protected that device is against solid objects (like dust and dirt), while the second number looks at how well the device can withstand liquids (like water and sweat).
This might lead you to believe that IP ratings are the same as ATM classifications with the addition of solids. However, this isn’t true at all.
IP ratings don’t really account for water pressure, which is why an ATM rating is a better way to determine whether a device is safe to take swimming, snorkelling or diving.
This is also why you’re more likely to see the term ATM on the spec sheet of a smartwatch or fitness tracker than you are something not designed to withstand large amounts of water pressure, like a smartphone.