I have been using this on both my iPhone and iPad for some time. The default iOS configuration is to show the remaining battery charge as just a bar graph within the icon of a battery. While this gives you a general idea of how much charge remains, you can set iOS to show you an actual percentage of the remaining charge.
This is a simple setting to change. Open the Settings App >> General >> Usage. Toggle the ‘switch’ next to ‘Battery Percentage’ to ‘On’. From now on not only will the icon show you your remaining battery charge, but a percentage will appear to the left of the battery icon as well.
I find this to be much more useful as I keep an eye on the remaining battery charge throughout the day.
See my other iOS articles