How do I check my Apple Watch battery?

To find out more about your Battery Health on your watch, go to Settings/Battery/Battery Health.

If it is below 80%, the battery need to be replaced.

Charge Apple Watch - Apple Support

Apple Watch Service and Repair - Apple Support

Hello, I assume that you are using the latest WatchOS 11 , so here is my answer pertaining to that:

There are a couple of quick ways to check your Watch battery-

1. The quickest way to check it when using any watch face is to click the side button once to open control center, where by default you should be able to see the watch battery percentage. Click it once to hide it and return to your watch face.
2. The second convenient way to check your battery quickly and with a glance is to set it as a complication in the watch faces that support the complications feature.

I hope this answer proved of some help to you. Have a good day ahead!

@AnirudhsMac:

The Apple Watch 3 can not be upgraded to watchOS 11.