According to Google, the Pixel Watch comes with 24-hours of battery life. Obviously this is only a guide because depending on how you use your watch, you may get more or less than what Google claims.
For those who are finding that they are getting less than 24 hours and are wondering what’s up, Google has actually published some details on its support page where they show users what kind of activities will get them 24-hours of battery on the Pixel Watch. According to Google:
Now, honestly it would not be realistic to count how many times you check your watch for the time or receive notifications. In fact, we would actually discourage you from counting since it seems like a waste of time, but if you are finding you are getting less than ideal battery life, you could consider disabling some notifications you may not need, or maybe use your phone instead of your watch for mapping.