ATM ratings are used as an international guide to show water resistance for fitness gadgets and smartwatches. Each individual ATM rating shows you the number of ‘atmospheres’ of pressure that a device can handle when it’s motionless underwater. Every 10m of depth equals one atmosphere of pressure, so a smartwatch with a 5 ATM rating is designed to be water resistant to up to 50 metres in depth (for 10 minutes).
However, even if you have a smartwatch with a high ATM rating, remember that activities such as water-skiing or jet-skiing may damage your device. It’s best to stick to low-impact activities, like swimming in shallow water.
ATM ratings may sound similar to IP ratings, but the two ratings are different. ATM ratings show how deep the device can go in water and the water pressure it can withstand, and IP ratings show how water resistant a device is. The most commonly-used IP ratings are IP67 and IP68.
Here’s what different ATM definitions mean: