This isn’t an uncommon problem after installing any update to an iPhone or iPad, and is usually fixed by shutting it down, leaving it a minute or two, and then starting it up again.
If that doesn’t restore battery life, spend some time in Settings > Battery to discover the cause. In the past, it was often recommended that you try a full charge–discharge cycle to “recondition” your battery, but with more recent batteries and improved management that’s no longer thought to achieve much. What’s more likely to bring a solution is to watch the list of apps using up your battery the most. Following an update to iOS or iPadOS, settings may get changed, or bugs in an app can lead to excessive energy use. Over a few days, watch the apps at the top of the list, and check their settings, whether they’ve started getting your location all the time instead of only when active, and their notifications.