Newer MacBooks, including MacBook Pro and Air models, are designed to charge quickly up to 80 percent of their full capacity, and then switch to "Trickle charge" mode. This keeps the battery charging much more slowly for that last 20 percent, so you can leave your MacBook plugged in for a long time, such as overnight, without overcharging it. This applies to most MacBook models with built-in batteries, from around mid-2009 and later.
The time to get your MacBook to 80 percent of its full charge capacity will vary according to the MacBook model, but a new battery straight from the factory will take approximately 30 to 120 minutes, depending on size and use. For example, your MacBook charges faster in "Sleep" mode or off than it does when powered on or in use. At 80 percent of its full charge you can unplug and use the computer on battery power if you wish, or you can continue charging it to 100 percent battery capacity. Since charging slows to a trickle after it reaches the 80 percent mark, you will need to wait approximately two hours beyond the 80 percent charge time until the battery is completely full. This figure also varies by model, battery size and how new your battery is, and Apple makes no guarantees about specific charging times.
Rather than relying on a clock, use the MacBook's built-in indicators to tell you how long to charge it before using the battery. Depending on your model, you may have a light on your power adapter or lights on the MacBook itself that indicate battery charge. On the adapter, an amber light indicates that the MacBook is still charging, while green indicates the computer is charged and ready to use on battery power. Computer-based indicator lights vary, so consult your MacBook's user guide. If your computer is on, the battery icon appears in the upper right corner. If the percentage of charge does not show beside it, you can turn that option on in the "System settings." You can also hover your mouse pointer over the battery icon to make your computer display its current charge.
If your MacBook has a removable battery, as in most pre-2009 models, you may need to do a calibration charge. The time required for this varies by model, but it will help you get the maximum usage out of your battery. Plug in your MacBook until it is fully charged, which can range from approximately three to five hours, and then let it rest for two additional hours. If the MacBook is off, it can be unplugged. If you plan to use it during these final two hours, keep it plugged in. After two hours of full capacity charging, you can unplug your MacBook and use it on battery power. After this first charge, the two-hour rest period is not necessary, although you may want to do it periodically to recalibrate the battery.