To quote the Apple notebook battery page, “The built-in battery of your MacBook Pro or MacBook Air is designed to deliver up to 1000 full charge and discharge cycles before it reaches 80 percent of its original capacity.”
Apple does not tell you how to find out what your current percentage is. FruitJuice can! We report “Factory Capacity Percent” as relative to the battery’s “original capacity” (as noted on that Apple page).
The FruitJuice Lifespan indicator (filled pie) shows how many charge and discharge cycles your battery has seen relative to the “1000 full charge and discharge cycles” noted on Apple’s page. For some machines, like first generation MacBook Air’s, this number is less than 1000. If you hover over either of these items on the Battery Information screen, you can see the actual numbers.