How long is a good nap?
When you feel sleepy, it is best to nap for 15-30 minutes. This will improve your alertness and concentration. It is often called a power nap. A short nap of this length may reduce the risk of falling asleep. Sleeping for a longer time is not as effective. After a long nap, you may wake up feeling groggy. This is called sleep inertia. It can make it more difficult to do things well. It may last for a few minutes but can last much longer. Having sleep inertia is more likely if you are not getting enough sleep at night, if you have taken a long nap, or if you have been woken suddenly from a deep sleep.