How long should a power nap be? What the nap studies found

It is mid-afternoon, the words on the screen have started to swim, and you have a choice. You can push on, reach for another coffee, or close your eyes for a few minutes. If you choose the last option, almost every guide will tell you the same thing: keep it short, ideally 20 minutes, so you wake up refreshed rather than groggy.

That advice is roughly right, but the research behind it is more specific, and in places more surprising, than the rule of thumb suggests. The best-known laboratory comparison found that 10 minutes of sleep beat 20 and 30. Naps of 30 or 90 seconds did nothing measurable. A large review questioned whether "30 minutes or less" reliably avoids grogginess at all. And the biggest meta-analysis of afternoon naps found that the benefit to test scores did not depend much on nap length.

Short answer: a power nap is a short daytime sleep, usually 10 to 20 minutes of actual sleep, taken to restore alertness. In controlled studies of people who had slept too little the night before, about 10 minutes of sleep gave the fastest lift, 20 minutes gave a lift that arrived a little later, and 30 minutes often brought a spell of grogginess before the benefit. Because these figures count minutes asleep, most people need to allow 5 to 15 extra minutes to fall asleep. Longer naps can help some kinds of learning but tend to leave you groggy for longer. Nap length matters less than timing, how much you slept the night before and what you need to do straight after waking.

What is a power nap?

A power nap is a brief, planned sleep during the day, usually in the early afternoon, that ends before you have been asleep long enough to reach deep sleep. The idea is to get some of the alerting benefit of sleep without the heavy, confused feeling that can follow waking from a longer nap.

That heavy feeling has a name: sleep inertia. It is the period of grogginess and reduced performance just after waking. It usually fades within minutes to half an hour, but while it lasts, reaction times are slower and thinking is less sharp. Most power nap advice is really advice about getting the benefit of sleep while keeping sleep inertia small.

The common explanation is that sleep inertia is worse when you wake from deep slow-wave sleep, and that short naps end before deep sleep begins. That explanation is partly supported, as we will see, but the timing of deep sleep varies a great deal from person to person and day to day.

How long should a power nap be?

The clearest evidence comes from a series of small laboratory studies at Flinders University in Australia. They are worth looking at closely, because they are the source of most of the numbers you see quoted.

The 5, 10, 20 and 30 minute comparison

In the best-known study, Brooks and Lack (2006) asked 24 healthy young adults, who were good sleepers and did not usually nap, to restrict their sleep to about 5 hours the night before. At 3 pm the next day, each person had either no nap or a nap of exactly 5, 10, 20 or 30 minutes of sleep, measured with EEG, and was then tested for 3 hours.

• 5 minutes of sleep produced few benefits compared with no nap.
• 10 minutes produced immediate improvements in sleepiness, fatigue, vigour and cognitive performance, and some of these lasted up to 155 minutes.
• 20 minutes produced improvements that began about 35 minutes after waking and lasted up to 125 minutes.
• 30 minutes produced a period of impaired alertness and performance immediately after waking, consistent with sleep inertia, followed by improvements lasting up to 155 minutes.

The authors concluded that 10 minutes was overall the most effective of the lengths they tested.

Why 30 or 90 seconds is not enough

An earlier study by the same group, Tietzel and Lack (2001), compared no nap, a 10-minute nap and a 30-minute nap in 12 young adults after a night of about 4.7 hours of sleep. The 10-minute nap brought an immediate improvement that lasted through the hour of testing. After the 30-minute nap, most measures first got worse and had only partly recovered by the end.

A follow-up, Tietzel and Lack (2002), then tested ultra-brief naps of 30 seconds and 90 seconds in 16 people. Neither produced any measurable improvement, while the 10-minute nap again did. So simply drifting off for a moment does not seem to be enough. Something that happens between about 90 seconds and 10 minutes of sleep appears to matter.

The 20-minute nap

The 20-minute rule has its own evidence. Hayashi, Watanabe and Hori (1999) had seven young adults nap at 2 pm and woke them 20 minutes after they first fell asleep. All were woken from light stage 2 sleep, not deep sleep. Compared with resting in a chair without sleeping, the nap improved sleepiness, performance and confidence in their own performance. This was a very small study, but it fits the Flinders results: 20 minutes can work well, with the benefit sometimes taking a little longer to arrive than after 10 minutes.

The detail most guides leave out

In these studies, the nap length is minutes of sleep, measured from the moment the EEG showed sleep onset. It is not minutes lying down. If you set a 10-minute alarm and take 8 minutes to fall asleep, you have had about 2 minutes of sleep, which is closer to the conditions that showed little or no benefit. In practice, a 10 to 20 minute power nap usually means setting an alarm for somewhere between 15 and 30 minutes, depending on how quickly you fall asleep in the afternoon.

Sleep in the nap	What the lab studies found	Main trade-off
Under 2 minutes	No measurable improvement in one study of 16 people	Feels restful, but little evidence of an alertness lift
About 5 minutes	Few benefits compared with no nap	Low risk, low return
About 10 minutes	Fastest improvement, lasting up to about 2.5 hours in one study	Best fit when you need to work soon after waking
About 20 minutes	Improvement arriving roughly half an hour after waking	Allow a short buffer before demanding work
About 30 minutes	Grogginess first, then improvement	Poor choice right before anything that needs a quick, clear head
60 to 90 minutes	Can include deep and REM sleep, which helped one kind of learning	Longer grogginess; needs a free block of time

Keep the limits of this table in mind. The results come from small samples of healthy young adults, mostly after restricted sleep, in laboratory conditions. They describe averages, not what will happen to you on a particular afternoon.

Does "30 minutes or less" really avoid grogginess?

Many workplace and safety guides say that naps of 30 minutes or less avoid sleep inertia. A review by Hilditch, Dorrian and Banks (2017) looked at whether the research supports that advice. They found that the literature on short afternoon naps is fairly thorough, but that results on when deep sleep begins, and on how long and how strong sleep inertia is after short naps, are mixed. The likely reasons are differences in how much people had slept beforehand and the time of day they woke up. Their conclusion was that a blanket recommendation without that context is potentially misleading, and that there is very little research on short naps taken at night.

In practical terms, a short nap lowers the risk of grogginess but does not remove it. If you slept badly last night, you may fall into deeper sleep faster than usual, and even a 20-minute nap can leave you foggy for a while.

What can you do about grogginess after you wake? A structured review of what the authors call reactive countermeasures, Hilditch, Dorrian and Banks (2016), found no convincing evidence base for any of them. Light and cooler temperatures looked promising for how alert people felt, but it was not clear whether they improved performance. The authors advised planning ahead and avoiding safety-critical tasks immediately after waking.

Do naps actually improve thinking?

Individual experiments are small, so meta-analyses that pool many studies are the better guide to the overall effect.

• Leong, Lo and Chee (2022) combined 60 samples from 54 studies of afternoon naps. Overall, naps had a small to medium benefit across cognitive tests (Cohen's d about 0.38). Benefits appeared for memory, vigilance and speed of processing. Notably, the effect did not significantly change with age, nap length, start time, whether people napped habitually, or whether they had slept less the night before. Most of the samples (52 of 60) tested memory, which is a different question from how alert you feel in the first minutes after waking.
• Dutheil and colleagues (2021) pooled 11 studies with 381 working-age adults. The average nap was about 55 minutes. Overall performance improved after napping, with a small effect (0.18) that was larger for alertness (0.29). The benefit was clearest up to about 2 hours after the nap, and results were conflicting during the sleep inertia period. Early afternoon naps tended to do better. The authors noted that almost all of the studies were run in laboratories and called for research in real working conditions.

Put together, the evidence suggests that a nap usually helps afterwards, but by a modest amount, and that length is not the main thing that decides whether it helps. Length mostly decides how soon the benefit arrives and how much grogginess you have to get through first.

Longer naps and learning

A long nap is not simply a failed power nap. In a well-known study, Mednick, Nakayama and Stickgold (2003) found that naps of 60 to 90 minutes containing both deep slow-wave sleep and REM sleep improved performance on a visual texture task about as much as a full night of sleep did. That is one specific perceptual learning task, but it shows that the right nap length depends on the goal. If you need to feel sharp for a meeting in 20 minutes, a short nap fits. If you have a free afternoon after an intense learning session, a longer nap may serve a different purpose, at the cost of more grogginess on waking.

You may see the advice to nap for "one full 90-minute sleep cycle". Sleep cycles do run very roughly that long, but their length varies between people and across the night, so a 90-minute nap is an approximation, not a guarantee that you will wake at a light point.

Habitual nappers and first-time nappers

Most of the duration studies above recruited people who did not usually nap. That matters. In a study by Milner, Fogel and Cote (2006), both habitual and non-habitual nappers felt more alert after a short nap. But on a motor learning task, performance got worse for the non-habitual nappers who napped and improved for everyone else, including non-habitual nappers who spent the time reading. The sample was small, and the effect was on one type of task. Still, it suggests that if you rarely nap, your first few attempts may feel different from the results reported for regular nappers, and it is worth testing before you rely on a nap before something important.

The coffee nap

A "coffee nap" means having caffeine immediately before a short nap. The reasoning is that caffeine takes a while to take effect, so you can nap before it arrives and then wake up to both effects together.

Two laboratory studies tested the combination.

• In a driving simulator, Reyner and Horne (1997) gave 12 sleepy participants a 30-minute break before a 2-hour monotonous afternoon drive. Driving incidents fell to 34% of placebo levels with caffeine alone, and to 9% with caffeine plus a nap of under 15 minutes. Even participants who only dozed without falling fully asleep still benefited.
• Hayashi, Masuda and Hori (2003) compared a 20-minute nap on its own with the same nap combined with caffeine beforehand, bright light afterwards or face washing afterwards, in 10 young adults. Caffeine plus nap was the most effective for sleepiness and performance over the following hour. Bright light came close except on performance, and face washing had a mild, short-lived effect.

These were small studies with sleepy young adults, and they used a fixed caffeine dose. People react to caffeine very differently, and it can affect sleep later in the day, so this is a description of research findings rather than a recommendation. If you do not use caffeine, the bright light result is a reasonable alternative to test.

How to take a power nap

Based on the studies above, here is a practical approach for a working day.

1. Decide what the nap is for. If you need to be alert for work soon after, aim for about 10 to 20 minutes of sleep. If you have a long free block and the goal is recovery after intense learning, a longer nap is an option, but plan for grogginess.
2. Nap early in the afternoon. Studies used naps from about 12:40 pm to 3 pm, and the Dutheil meta-analysis found earlier afternoon naps tended to do better. This also matches the post-lunch dip many people notice, covered in our guide to the afternoon slump.
3. Set the alarm for sleep plus settling time. If you usually drift off in about 5 minutes, a 15 to 20 minute alarm gives roughly 10 to 15 minutes of sleep. If you take longer to fall asleep, allow more.
4. Lower the cost of failing to fall asleep. Even if you do not fall fully asleep, light dozing may still help, as the driving study found. Lying quietly with your eyes closed is also a reasonable break in itself.
5. Give yourself a buffer. Do not schedule anything that needs a quick, clear head in the first 10 to 15 minutes after waking, especially after a longer nap. Light, routine tasks are a better way to come back.
6. Get light after waking. Moving into daylight or bright light is a low-cost option with some supporting evidence for how alert you feel.

A nap is not the only way to recover in the middle of the day. If you are not actually sleepy but your attention is tired, a walk outdoors or a real screen break may do more. Our guides to brain breaks for adults and attention restoration theory cover those options, and ultradian rhythms looks at whether there is a natural cycle to plan breaks around.

A two-week nap test

Because the averages hide large individual differences, the most useful evidence is your own. Here is a simple test.

1. Pick a regular slot. Choose an early afternoon time on workdays when you could nap without disrupting anyone.
2. Alternate three conditions. On different days, try a short nap (alarm at about 20 minutes), a non-sleep break of the same length (a walk, or sitting quietly without a screen) and no break.
3. Rate yourself twice. Note how alert you feel on a 1 to 10 scale just before the slot, and again 30 and 90 minutes later. Also note how long it took to fall asleep and how groggy you felt on waking.
4. Track one concrete output. Pick something you can count for the hour after the slot: pages edited, tickets closed, errors caught or a short focus task like the one in our attention span test.
5. Note your night. Record roughly how long you slept the night before, because nap effects in the research were often largest after short nights.
6. Compare after two weeks. Look at whether the nap days beat the break days, and whether the result depended on the previous night. Also check whether naps changed how easily you fell asleep that evening.

Some people find a nap clearly helps. Others find a walk does the same job without the grogginess. Either answer is useful.

Where Zone fits

Zone is a pair of EEG earbuds with an app that shows app brain states: In Flow, Locked In, Running Hot, Drifting and Depleted. The earbuds read signals through an in-ear EEG array, which our article on in-ear EEG explains. Depleted is the app's estimate that your mental energy has run low against your own baseline, and Drifting is its estimate that engagement has dropped while energy holds, the pattern behind much mind wandering.

These app states are not a measure of sleepiness, and the app does not tell you whether a nap, a walk or a change of task is the right choice. What it can add to the two-week test is a second record. You can compare session summaries from the hour after nap days with those after break days and no-break days, and see whether, for example, Depleted appeared less often after one kind of break. Our guide to focus tracking explains how sessions work. Treat these as app estimates, and keep your own ratings and output counts as the main evidence. If you are regularly so sleepy during the day that you need to nap to function, that is worth raising with a qualified professional. Zone does not diagnose, treat, or manage any medical condition.

Common questions

How long is a power nap?

Usually 10 to 20 minutes of actual sleep. In the best-known comparison, 10 minutes of sleep gave the quickest improvement in alertness and performance, while 30 minutes brought grogginess first.

Is a 20-minute power nap good?

Yes, for most people it is a reasonable choice. Studies found that 20 minutes of sleep improved alertness and performance, although the improvement sometimes took around half an hour to appear. Remember that 20 minutes of sleep usually means a longer alarm.

Why do I feel worse after a nap?

That is sleep inertia, the grogginess after waking. It is more likely after longer naps, after short nights and when you wake from deeper sleep. It usually passes within minutes to half an hour. Bright light may help you feel more alert.

Is a 90-minute nap better than a 20-minute nap?

It depends on the goal. A 60 to 90 minute nap with deep and REM sleep improved one kind of perceptual learning as much as a night of sleep. But longer naps usually mean more grogginess on waking and need a larger free block of time. For a quick lift during a workday, a short nap fits better.

What is a coffee nap?

Taking caffeine just before a short nap. In two small laboratory studies, caffeine plus a short nap reduced sleepiness and improved performance more than either a nap or caffeine alone. People respond to caffeine differently, and it can affect sleep later in the day.

What time should I take a power nap?

Early afternoon is the most studied window, roughly between lunch and 3 pm. One meta-analysis found early afternoon naps tended to give better cognitive results.

Do power naps work if I slept well?

Many of the duration studies used people who had slept too little the night before. The largest meta-analysis found that the benefit of afternoon naps did not depend significantly on prior sleep restriction, but the effect is modest, so test it for yourself.

Sources

1. Brooks, A., and Lack, L. (2006). A brief afternoon nap following nocturnal sleep restriction: which nap duration is most recuperative? Sleep, 29(6), 831 to 840. DOI
2. Tietzel, A. J., and Lack, L. C. (2001). The short-term benefits of brief and long naps following nocturnal sleep restriction. Sleep, 24(3), 293 to 300. PubMed record
3. Tietzel, A. J., and Lack, L. C. (2002). The recuperative value of brief and ultra-brief naps on alertness and cognitive performance. Journal of Sleep Research, 11(3), 213 to 218. PubMed record
4. Hayashi, M., Watanabe, M., and Hori, T. (1999). The effects of a 20 min nap in the mid-afternoon on mood, performance and EEG activity. Clinical Neurophysiology, 110(2), 272 to 279. PubMed record
5. Hilditch, C. J., Dorrian, J., and Banks, S. (2017). A review of short naps and sleep inertia: do naps of 30 min or less really avoid sleep inertia and slow-wave sleep? Sleep Medicine, 32, 176 to 190. PubMed record
6. Hilditch, C. J., Dorrian, J., and Banks, S. (2016). Time to wake up: reactive countermeasures to sleep inertia. Industrial Health, 54(6), 528 to 541. PubMed record
7. Leong, R. L. F., Lo, J. C., and Chee, M. W. L. (2022). Systematic review and meta-analyses on the effects of afternoon napping on cognition. Sleep Medicine Reviews, 65, 101666. PubMed record
8. Dutheil, F., Danini, B., Bagheri, R., Fantini, M. L., Pereira, B., Moustafa, F., Trousselard, M., and Navel, V. (2021). Effects of a short daytime nap on the cognitive performance: a systematic review and meta-analysis. International Journal of Environmental Research and Public Health, 18(19), 10212. PubMed record
9. Mednick, S., Nakayama, K., and Stickgold, R. (2003). Sleep-dependent learning: a nap is as good as a night. Nature Neuroscience, 6(7), 697 to 698. PubMed record
10. Milner, C. E., Fogel, S. M., and Cote, K. A. (2006). Habitual napping moderates motor performance improvements following a short daytime nap. Biological Psychology, 73(2), 141 to 156. PubMed record
11. Reyner, L. A., and Horne, J. A. (1997). Suppression of sleepiness in drivers: combination of caffeine with a short nap. Psychophysiology, 34(6), 721 to 725. PubMed record
12. Hayashi, M., Masuda, A., and Hori, T. (2003). The alerting effects of caffeine, bright light and face washing after a short daytime nap. Clinical Neurophysiology, 114(12), 2268 to 2278. PubMed record