How Long Should a Power Nap Be? The 10-20 Minute Rule and the NASA Nap

The short answer: a power nap should be about 10 to 20 minutes of sleep, taken in the early afternoon. That's long enough to feel sharper and short enough that you wake up before deep sleep makes you groggy. If you've got a little more time, NASA's famous "26-minute nap" is about the upper limit. Somewhere past 30 minutes, you start to risk waking up feeling worse than before.

The length is the easy part. The hard part is waking up on time. This guide covers what the research actually found, the best time of day to nap, the "coffee nap" trick, and how to stop a 20-minute nap from turning into a 90-minute one.

Nap length: what to expect

The most useful study here is a 2006 experiment by Amber Brooks and Leon Lack, published in the journal Sleep. Twenty-four healthy young adults were limited to five hours of sleep, then took an afternoon nap at 3 pm of 5, 10, 20 or 30 minutes, or no nap at all (Brooks & Lack, 2006).

Nap length	What happened in the study
5 minutes	Little benefit compared with no nap
10 minutes	Immediate improvements in sleepiness, fatigue, vigour and mental performance, lasting about 155 minutes
20 minutes	Improvements too, but they showed up about 35 minutes after waking
30 minutes	A spell of grogginess first, then benefits lasting about 155 minutes

The researchers concluded that the 10-minute nap was the most effective overall. That fits what sleep doctors recommend. At Cleveland Clinic, sleep specialist Dr Nancy Foldvary-Schaefer puts the ideal nap at 15 to 20 minutes and says that for most people it's best to nap for less than an hour (Cleveland Clinic).

Rule of thumb:

• 10 to 20 minutes: the classic power nap. Best when you need to get straight back to work.
• Around 25 minutes: fine if you can allow a few minutes to come round afterwards.
• 30 to 60 minutes: the risky zone. You're more likely to wake from deep sleep and feel foggy.

Why longer naps make you groggy

The fog you feel after a long nap has a name: sleep inertia. The longer you sleep, the more likely you are to drop into the deeper stages of sleep. Cleveland Clinic explains that deep sleep is harder to wake from, "which makes you feel groggy, confused and unrefreshed" (Cleveland Clinic).

Long naps can also eat into your night. If you sleep for an hour at 4 pm, you may not feel sleepy at bedtime, which makes tomorrow's afternoon slump worse.

The NASA nap: where "26 minutes" comes from

You'll often see "the NASA nap" quoted as the perfect nap. It comes from a study of long-haul airline pilots run by NASA Ames Research Center and published as a NASA technical memorandum. On trans-Pacific flights, one group of crew members was given a planned 40-minute rest period in the cockpit during the quiet cruise phase, while another group carried on as normal (NASA, Crew Factors in Flight Operations IX).

The pilots who rested fell asleep on 93% of the opportunities. They took an average of 5.6 minutes to fall asleep and slept for 25.8 minutes. The nap was linked to better alertness and performance, and the benefit lasted through the descent and landing. The Sleep Foundation summarises the results as a 54% increase in alertness and a 34% increase in performance compared with the pilots who didn't nap (Sleep Foundation).

So "26 minutes" wasn't a magic number the researchers set. It's roughly how long pilots actually slept in a 40-minute window. The practical lesson is just as useful: it takes a few minutes to fall asleep, so the time you lie down is not the time you're asleep.

Set your wake-up for nap length plus 5 minutes

Because most people need a few minutes to drift off, set your wake-up for the nap you want plus about five minutes:

You want to sleep for	Set your wake-up for
10 minutes	15 minutes after you lie down
20 minutes	25 minutes after you lie down
26 minutes (the NASA nap)	30 to 35 minutes after you lie down

If you didn't fall asleep at all, that's fine. Resting quietly with your eyes closed still gives you a break, and you'll often drift off faster tomorrow.

The best time of day for a power nap

Aim for the early afternoon. Most people feel a natural dip in alertness after lunch, and a nap then is less likely to affect your night. Dr Foldvary-Schaefer advises napping "earlier in the afternoon, like before 2 p.m. or 3 p.m." (Cleveland Clinic).

If you work nights or early starts, shift the same idea to your own day: nap well before your main sleep, not in the last few hours before it. For more on that, see our guide to sleeping days without missing shifts.

The coffee nap

A "coffee nap" sounds like a contradiction, but it's backed by research. You drink a coffee, then nap straight away. Caffeine takes a while to kick in, so you're asleep before it does and wake up as it starts working.

In a 1997 driving-simulator study, researchers Reyner and Horne gave sleepy volunteers a 30-minute break before a two-hour afternoon drive. Caffeine alone (200 mg) cut driving incidents to 34% of the placebo level. Caffeine plus a short nap cut them to 9% (Reyner & Horne, 1997).

The Sleep Foundation's version: about 200 mg of caffeine (roughly a 12-ounce coffee or two shots of espresso), drunk fairly quickly, followed by a nap of around 20 minutes. Caffeine's effects can last up to six hours, so don't do this late in the day. If caffeine doesn't agree with you, or you're pregnant or have high blood pressure, anxiety or insomnia, check with a doctor first (Sleep Foundation).

If you're driving and feel sleepy, stop. Pull over somewhere safe and take a break. A coffee nap can help you get through the rest of the journey, but it doesn't replace proper sleep.

How to take a good power nap

1. Decide the length before you lie down, and set the wake-up for that length plus about five minutes.
2. Nap before mid-afternoon if you sleep at normal hours.
3. Make it easy to drift off: somewhere quiet and dim, phone face down, an eye mask if you need one.
4. Lie back or recline. Sleeping fully under the duvet makes a short nap harder to end.
5. Get up as soon as you wake. Stand up, get some light and drink some water. Don't go back to sleep.
6. Make it a habit. If the afternoon slump hits every day, a nap at the same time each day is easier to keep short than a random one.

When a nap is a warning sign

An occasional nap is normal. Needing one every day just to get through is worth paying attention to. Dr Foldvary-Schaefer says "you shouldn't struggle to stay awake during the day", and constant daytime sleepiness can be a sign of a sleep disorder such as narcolepsy (Cleveland Clinic). If you're always tired despite a full night in bed, or you fall asleep without meaning to, talk to a doctor. For better night-time sleep, see our guide to sleep hygiene habits.

The hard part: actually waking up

Most power naps go wrong at the end. You turn off the alarm, think "two more minutes", and wake up an hour later in the worst kind of fog. Heavy sleepers know this well: a phone alarm is easy to dismiss without really waking up.

A phone call is harder to ignore. It rings like a real call, and you have to pick it up and listen to a voice. That's what ReminderIt does: it calls your phone at the time you choose and reads your reminder out loud, for example "Nap's over. Stand up and get some light." If you don't answer, the reminder arrives on WhatsApp instead.

You don't need an app. Just message ReminderIt on WhatsApp:

• "Call me in 25 minutes" for a one-off nap.
• "Call me every weekday at 1:30 pm to end my nap" if you nap at the same time each day.

For more on why calls work when alarms don't, see phone call alarms for heavy sleepers.

There's a 7-day free trial with 7 reminder calls (3 if your number is in a country where calls cost more to place, such as the UK). After that, it's one plan at $7 a month (₹299 in India), which includes 70 calls a month. That's enough for a weekday nap call plus your other reminders.

The short answer

Keep a power nap to 10 to 20 minutes of sleep, and set your wake-up for about five minutes longer to allow time to fall asleep. Nap in the early afternoon, before 2 or 3 pm. Up to about 25 minutes is fine (that's the NASA nap). Beyond 30 minutes, you're more likely to wake up groggy. For an extra boost, try a coffee before a 20-minute nap, but not late in the day. Most importantly, use a wake-up you can't sleep through.

Sources: Brooks A, Lack L, A brief afternoon nap following nocturnal sleep restriction: which nap duration is most recuperative?, Sleep, 2006; Rosekind MR et al., Crew Factors in Flight Operations IX: Effects of Planned Cockpit Rest on Crew Performance and Alertness in Long-Haul Operations, NASA Ames Research Center; Sleep Foundation, NASA Nap and What Is a Coffee Nap?; Reyner LA, Horne JA, Suppression of sleepiness in drivers: combination of caffeine with a short nap, Psychophysiology, 1997; Cleveland Clinic, How Long Should a Nap Be?. This article is general information, not medical advice.