While everyone you know swears by a certain magic number (7 minutes! No, 17 minutes!), the National Sleep Foundation has this to say: “a short nap”—say, 20 minutes—“can help to improve mood, alertness and performance,” without side effects like grogginess.
Feeling really experimental? Try napping after drinking coffee. Several studies have shown that if you caffeinate before as short nap of 15 to 20 minutes, you’ll wake feeling even perkier than usual, because caffeine takes about 20 minutes to kick in. As Vox put it, “coffee naps are better than coffee or naps.”
Whatever you do, please do not try to replace your evening sleep with napping. While it has plenty of benefits, 20 minutes of shuteye in the afternoon is nothing like a good night’s rest.