How long should a nap be? In people who sleep fine, about 10 to 20 minutes.
After a bad night, a short nap can put some energy back. In people who usually sleep fine, sleepiness and mental fog can lift for a couple of hours [1]. The catch is that the nap spends some of the sleep drive your body was building for tonight [2]. If you already have insomnia, skip it. That leftover tiredness is what is supposed to help you at bedtime.
Those numbers come from a study of 3pm naps for people who had about five hours of night sleep. The participants were 24 healthy young good sleepers who were not regular nappers [1]. They had one short night, then a timed afternoon sleep of 5, 10, 20, or 30 minutes, then three hours of testing. That is a useful map for a good sleeper who is dragging after a bad night.
Here is what each length did.
About 10 minutes. This is the length that helped fastest. Sleepiness, tiredness, energy, and thinking all improved as soon as they got up, and some of that lift was still there about two and a half hours later [1]. Five minutes of sleep did almost nothing next to staying awake. Ten minutes is long enough to take the edge off, and short enough that you are unlikely to wake from deeper sleep. The clock was minutes of actual sleep, not minutes on the couch: falling asleep takes a few minutes, so a timer set to 10 often ends before you have had a 10-minute nap.
About 20 minutes. This is the usual power nap. The lift did not show up right away. It arrived about 35 minutes after waking, then lasted up to about two hours [1]. If you have to be sharp the moment you sit up, this is a weaker match than 10 minutes. If you have a little time after you wake, 20 minutes bought a longer stretch of better alertness. It got popular because it is long enough to help and short enough to stay out of the groggy zone that shows up at 30.
About 30 minutes. People were worse right after they woke, then better, with gains lasting a couple of hours, similar to the shorter naps [1]. The extra ten minutes bought more sleep and a hangover. That first stretch of fog is sleep inertia: you woke while the brain was still coming up from deeper sleep. If you can sit still for a while after the timer, the dip passes and you still get the later lift. If you need to drive, talk, or think the moment you get up, 30 minutes is the wrong length. The 20-minute rule of thumb exists mostly to dodge this.
An hour or more. A long nap spends more of the sleep drive your body has been building since morning [2]. You may feel more recovered in the afternoon, and you are likelier to wake from deeper sleep, which is why these naps often leave you groggy for a stretch. Length and clock both matter. A short nap early in the afternoon is not the same as a long one close to bed [3]. An early-evening nap has been shown to make that night slower to start and lighter once it does, because some of the pressure has already been spent [4]. The 10, 20, and 30 minute numbers above do not apply here. Those lengths were not tested at an hour.
If you already have insomnia, it is better not to have a nap at all. A nap of any length spends at least some of the pressure that was supposed to help you sleep tonight [2, 5], working against your goal to sleep well at night. Rest counts any daytime sleep as a nap: a doze at your desk, twenty minutes on the sofa, an hour in bed. Find out which is the only exception to this rule in our full article: Why napping can keep insomnia going.
If nights have been off for months, skip the timer. See how Rest can help »
Citations
Brooks, A., & Lack, L. (2006). A brief afternoon nap following nocturnal sleep restriction: which nap duration is most recuperative? Sleep, 29(6), 831–840. https://doi.org/10.1093/sleep/29.6.831 — in 24 healthy young good sleepers, a 5-minute nap did little; 10 minutes helped immediately (some benefits out to 155 minutes); 20 minutes helped after about 35 minutes (benefits out to 125 minutes); 30 minutes impaired alertness at first, then helped (out to 155 minutes). Lengths were minutes of sleep, not minutes in bed.
Borbély, A. A., Daan, S., Wirz-Justice, A., & Deboer, T. (2016). The two-process model of sleep regulation: A reappraisal. Journal of Sleep Research, 25(2), 131–143. https://doi.org/10.1111/jsr.12371 — sleep drive builds during wake and is discharged during sleep.
Milner, C. E., & Cote, K. A. (2009). Benefits of napping in healthy adults: Impact of nap length, time of day, age, and experience with napping. Journal of Sleep Research, 18(2), 272–281. https://doi.org/10.1111/j.1365-2869.2008.00718.x — in healthy adults, short or early naps are not equivalent to long or late ones.
Werth, E., Dijk, D. J., Achermann, P., & Borbély, A. A. (1996). Dynamics of the sleep EEG after an early evening nap: experimental data and simulations. American Journal of Physiology, 271(3), R501–R510. https://doi.org/10.1152/ajpregu.1996.271.3.R501 — after an evening nap, the following night had a longer time to fall asleep and less deep-sleep EEG activity.
Perlis, M. L., Smith, M. T., Benson-Jungquist, C., & Posner, D. A. (2005). Cognitive Behavioral Treatment of Insomnia: A Session-by-Session Guide. New York: Springer. https://doi.org/10.1007/0-387-29180-6 — stimulus control includes not napping, so last night's lost sleep can help you the next night.