Apple Watch Battery Life
How long should an apple watch run if charged over night
Apple Watch
Apple says 18 hour or so. (The Ultra has a bigger battery, is fatter and heavier, and it lasts longer.) It depends on use, of course. If you do lots of hiking requiring the GPS to be used a lot, the time may be shorter. I exercise some every day, and it might be down to 40% when I go to bed.