How long does the iPhone 15 battery actually last in everyday use?

My iPhone 15 easily gets me through a whole day with normal use if I'm not constantly scrolling. If you take a lot of photos or watch videos, you'll notice the battery draining faster - sometimes it's only 18 to 20 hours. With lighter use (mostly messaging and a bit of browsing) you can stretch it to two days, but that's pretty much the exception.