How long should a power nap be?
The research counts from the moment you fall asleep
- For an afternoon nap, aim for 10 to 20 minutes of actual sleep.
- Past about 30 minutes, you are more likely to wake up groggy (sleep inertia).
- The research counts from the moment you fall asleep. A timer started when you lie down spends part of your nap on falling asleep.
Where the "10 minutes" and "20 minutes" come from
The study most often behind nap-length advice is a 2006 experiment at Flinders University in Australia. Twenty-four healthy young adults had their night's sleep cut to about five hours, then took a 3 p.m. nap of 5, 10, 20 or 30 minutes, compared against a day with no nap.
Nap length in that study was counted from sleep onset, as measured by EEG. The results:
- 5 minutes: little benefit over no nap
- 10 minutes: immediate improvement in sleepiness, fatigue and cognitive performance, lasting about 155 minutes
- 20 minutes: improvements, but they took about 35 minutes after waking to show up
- 30 minutes: a period of grogginess right after waking before the benefits appeared
That is why you will read that 10 minutes is the most efficient nap. It means 10 minutes asleep.
NASA's well-known pilot study works the same way. Long-haul pilots were given a 40-minute rest period in the cockpit and slept an average of 26 minutes of it. Those who napped showed 34% better performance and up to 54% better alertness than those who did not. The famous "26 minutes" is how much of a 40-minute window was actually sleep.
Falling asleep comes out of your nap
A 2023 meta-analysis of 110 cohorts and 4,058 healthy adults found that people lying down to nap during the day took about 12 minutes on average to fall asleep.
So a regular 20-minute timer started when you lie down buys you about 8 minutes of sleep. And it changes day to day: after a short night you might be out in 3 minutes, after a coffee it could take 15 or more. The same 20-minute timer gives you a different nap every time.
Why longer is not better
Once a nap runs long enough to reach deeper sleep, waking up from it is harder, and that grogginess can cancel out the point of the nap. In the Flinders study it already appeared at 30 minutes. Long or late naps can also make it harder to fall asleep that night.
How to take a better nap
- Aim for 10 to 20 minutes asleep. 10 if you need to be sharp right away, 20 if you have a little time to come around.
- Budget for falling asleep. With a regular timer, add your usual time to fall asleep. Just know it will not be the same every day.
- Keep it under 30 minutes. And keep long naps out of the evening if they affect your night.
- Always set an alarm. It is what keeps "just a few minutes" from turning into an hour.
A timer that waits for you to fall asleep
NapSense is a nap timer built around this exact problem. Hold your phone or keep it next to you on the bed, and it starts counting once the phone goes still. Set 20 minutes and the alarm rings 20 minutes after you drift off.
To be clear about what it measures: NapSense watches for your phone to stop moving, not your brain waves, so its idea of "asleep" is not a sleep lab's. What it does is wait instead of counting from the moment you tap start. No account, and your data stays on your phone.
Get NapSense on the App Store (free)References
- Brooks A, Lack L. A brief afternoon nap following nocturnal sleep restriction: which nap duration is most recuperative? Sleep. 2006;29(6):831–840.
- Rosekind MR, et al. Alertness management: strategic naps in operational settings. Journal of Sleep Research. 1995;4(S2):62–66.
- Iskander A, Jairam T, Wang C, et al. Normal multiple sleep latency test values in adults: a systematic review and meta-analysis. Sleep Medicine. 2023. PubMed
This article is general information, not medical advice. If you are persistently very sleepy during the day, talk to a doctor.