Updated
For most adults, the best power nap is 10 to 20 minutes, taken in the early afternoon. That is long enough to take the edge off sleepiness and short enough that you usually wake before falling into deep sleep, so you can get back to work without a long spell of grogginess. Set the alarm for about 20 to 25 minutes after you lie down to leave time to drift off.
Naps of around 30 minutes to an hour are more likely to leave you groggy right afterward, because you may wake from deeper sleep. A nap of about 90 minutes is the other workable option when you have the time, since it can cover a full sleep cycle, but it is more likely to affect how you sleep that night.
What the nap studies found
The most cited study on nap length is a 2006 paper in the journal Sleep by Brooks and Lack at Flinders University in Australia. After restricting participants' sleep the night before, they compared afternoon naps of 5, 10, 20, and 30 minutes with no nap. The 10 minute nap came out as the most effective overall, with benefits to alertness and performance that showed up right away. The 20 minute nap also helped, but its benefits took longer to appear. The 30 minute nap was followed by a period of impaired alertness and performance immediately after waking, the classic sign of sleep inertia.
You have probably also heard of the NASA nap. In a study of long haul airline crews led by Mark Rosekind at NASA Ames Research Center and published by NASA in 1994, pilots were given a planned 40 minute rest period in the cockpit during the cruise phase of a flight. They slept for about 26 minutes on average, and the nap was linked with better alertness and performance than in crews who did not rest. It is a real finding, but it comes from pilots on long haul flights, so treat it as evidence that short naps help tired people rather than as a precise recipe.
Mayo Clinic's guidance for healthy adults lines up with both: aim to nap for only 10 to 20 minutes, and take naps in the early afternoon, because napping after 3 p.m. can interfere with sleep at night.
Why longer naps can make you feel worse
Sleep inertia is the groggy, slow, sometimes irritable state right after waking. A review in Sleep Medicine Reviews by Tassi and Muzet in 2000 reported that waking abruptly from slow wave sleep, the deepest stage, is associated with more sleep inertia than waking from lighter stages. The longer you nap, the more likely you are to slip into that deep sleep before the alarm.
That is why a 45 minute nap can feel like a mistake. You wake up halfway through a cycle, from deep sleep, and spend the next half hour feeling worse than before you lay down. If you are already short on sleep, you may reach deep sleep sooner, which makes short naps even more important.
Picking the right nap for your situation
The 10 to 20 minute power nap. The everyday choice. It works at a desk, in a car you are not driving, or on a sofa, and you can get straight back to what you were doing.
The 90 minute nap. If you have a free afternoon and slept badly, a nap of around 90 minutes can take you through a full cycle, including deep and REM sleep, so you are more likely to wake from lighter sleep at the end. The trade off is time and the chance that you will be less sleepy at bedtime.
The pre shift or pre drive nap. Before a night shift or a long drive, a short nap can help if you are sleepy, but allow time for any grogginess to clear before you take the wheel. If you are drowsy while driving, pull over somewhere safe.
The nap to avoid. Long naps late in the afternoon or in the evening are the ones most likely to push your bedtime later. Mayo Clinic also notes that if you have insomnia or poor sleep at night, napping might make those problems worse.
How to take a better power nap
- Set an alarm before you close your eyes. For a 15 to 20 minute nap, set it for about 20 to 25 minutes, since it usually takes a few minutes to fall asleep.
- Lie down or recline if you can. Sleep comes more easily when your head is supported.
- Make it dark and quiet. An eye mask and earplugs, or a low steady sound, help in an office or on a train.
- Do not worry if you do not fully fall asleep. Lying still with your eyes closed for 15 minutes still gives you a break.
- Get up when the alarm rings. Resist the urge to extend it, which is how a 20 minute nap turns into an hour and a groggy afternoon.
- Get light and move a little afterward. Stand up, splash water on your face, or step outside for a minute to clear the fog.
When frequent napping is a signal
An occasional nap is normal. Needing a nap every day to get through, or falling asleep without meaning to, often means you are not getting enough sleep at night. The American Academy of Sleep Medicine and the Sleep Research Society recommend at least seven hours a night for adults. If you get that and still struggle to stay awake during the day, it is worth talking to a doctor.
Napping with Snora
Snora has a free nap timer on the Sleep tab. You pick a duration, Snora counts it down, and an alarm wakes you at the end, so you do not have to set and delete a regular alarm each time. The nap timer is free, like alarms and sleep tracking.
FAQ
How long should a power nap be?
For most adults, 10 to 20 minutes. A 2006 study in Sleep found a 10 minute afternoon nap was the most effective of the lengths tested, and Mayo Clinic recommends 10 to 20 minutes for healthy adults. Set the alarm a few minutes longer than that to allow time to fall asleep.
Is a 30 minute nap too long?
It can be. In the same 2006 study, a 30 minute nap was followed by a period of grogginess and lower performance right after waking. If you have only half an hour, aim to sleep for around 20 minutes of it.
Is a 90 minute nap better than a 20 minute nap?
It depends on your goal. A 90 minute nap can cover a full sleep cycle, so you are more likely to wake from lighter sleep, which suits a free afternoon after a bad night. A 20 minute nap is easier to fit into a workday and less likely to affect your sleep that night.
What is the best time of day to take a nap?
Early afternoon is usually best. Mayo Clinic advises napping in the early afternoon and notes that napping after 3 p.m. can interfere with nighttime sleep.