Why twenty minutes
A short nap is one of the quickest ways through an afternoon slump. The trick is the length. Around twenty minutes is long enough to take the edge off tiredness and short enough to wake before you sink into deep sleep, which is what leaves you groggy after a longer nap.
That grogginess has a name, sleep inertia, and after waking from deep sleep it can take up to half an hour to shake off. Keeping the nap short, and waking slowly rather than to a blaring alarm, is how a power nap leaves you sharper instead of worse.
How to use this nap timer
Lie down somewhere quiet and press Start. A calm voice gives you a minute to get comfortable and two more to let go, then the twenty-minute nap begins. If sleep does not come, lying still with your eyes closed still helps. At the end a soft chime and the voice bring you back slowly and talk you through sitting up, twenty-five minutes in all.
Keep this tab open and your device awake: a browser cannot keep time once the page is closed. On a phone, the Timer AI app is the surer choice, since it keeps running with the screen locked.
Three tips for a better power nap
Nap early in the afternoon
The post-lunch dip, roughly between one and three, is when a nap comes most easily. Napping late in the day can make it harder to fall asleep at night.
Try a coffee nap
Drink a coffee just before you lie down. Caffeine takes around twenty minutes to kick in, so it starts working at about the time you wake. Skip it if caffeine keeps you up at night.
Make it dark and quiet
An eye mask, or even a jumper over your eyes, helps more than you would expect. If the room is noisy, earplugs or a steady background sound make it easier to drift off.
Who it is for
Anyone who hits a wall in the afternoon: shift workers, new parents, students between lectures, people working from home who can steal twenty minutes on the sofa. It is also a good reset before a long drive or an evening that will run late.
A regular nap does not replace a good night's sleep. If you find you need one every day just to get by, that is worth taking seriously and raising with a doctor.