coconutBattery is a tool that shows you the current maximum capacity of your laptop’s battery in relation to the original capacity your battery had when it left the factory. You also get information about the battery: loadcycles (how often did you fully load your battery), the current charger (coconutBattery warns you if you plugged in a wrong charger for your laptop) and information about the age of your Mac. coconutBattery is not something you’ll necessarily use on a regular basis, but it’s a great tool to periodically check the condition of you battery.
Here is a screen shot of what coconutBattery shows you. Notice the Current Battery Capacity section. This battery is capable of holding a charge that is 91% in relation to when it was new: