iOS always shows the current battery usage with a dynamic battery icon, we can not directly know how much remaining battery in the current. Here is a little tips maybe you still don’t know, you can simply enable the Battery percentage in Settings app, and if your device is still jailbreak-able, then you can install some cydia tweaks to change the form of battery indicator, to get more battery info. However, if you have installed the latest iOS 7, then the most you can tweak the system settings to display a battery percentage in the status bar, without any jailbreak tweaks.
If you want to learn more details, please check out the below tutorial.
How to Display the Battery Percentage in Status bar
Step 1: Go to Settings app -> General -> Usage
Step 2: Scroll down to find out the BETTERY USAGE option, turn on the “Bettery Percentage” switch to make it into green.
Done, you will see a detailed digit percentage in the battery icon left. If you feel this feature is not necessary, then simply click the switch just mentioned above to turn it off.