FREE TOOL · POWER NAP · FULL CYCLE · FOR ADULTS
Nap calculator: when to wake up from a nap
Pick when you nap and a 20-minute power nap or a 90-minute full cycle. Get your alarm time, a matching timer and a warning if it is too close to bedtime.
Power nap · 20 min
Set your alarm for 1:55 PM
25 min in bed: about 5 min to fall asleep (an assumption) + 20 min of sleep.
- Lie down1:30 PM
- Asleep about1:35 PM
- Wake up1:55 PM
Good timing: it ends 8 h 35 min before your 10:30 PM bedtime.
Short enough to stay in light sleep, so most people wake up without much grogginess.
The short answer
For a quick boost, nap 10 to 20 minutes; to sleep through a full cycle, nap about 90 minutes. Add a few minutes to fall asleep, so a 20-minute power nap that starts at 1:30 p.m. needs an alarm at about 1:55 p.m. Nap in the early afternoon and finish at least 8 hours before bedtime.
How long should a nap be?
For alertness, 10 to 20 minutes of sleep is the sweet spot: long enough to help, short enough to wake up without much grogginess. About 90 minutes lets you sleep through a full cycle, which can help after a very short night. Naps longer than about 30 minutes are more likely to leave you groggy at first.
| Goal | Nap length | What to expect |
|---|---|---|
| Quick lift, back to work at once | 10 minutes | In a sleep lab study after a short night, a 10-minute nap improved alertness and performance straight away. |
| Power nap for the afternoon | 20 minutes | Helped in the same study, with the benefit showing about half an hour after waking. |
| Planned rest on a long shift | About 25 minutes of sleep in a 40-minute rest | What NASA’s long-haul pilots got in their planned cockpit rest (see below). |
| Avoid if you need to be sharp soon | 30 to 60 minutes | More likely to wake you from deeper sleep: a 30-minute nap caused grogginess first, then helped. |
| Make up for a very short night | About 90 minutes | Time for a full cycle of light, deep and REM sleep. Long, so it needs an early start to finish 8 hours before bed. |
Set the alarm for the nap plus the minutes you need to fall asleep. The calculator above adds 5 minutes by default and shows it as an assumption, because it varies from person to person.
What the NASA nap study found
The “NASA nap” comes from a study of long-haul flight crews published by NASA in 1994 (Rosekind and colleagues). Twenty-one pilots flying overnight across the Pacific took part. Twelve were given a planned 40-minute rest in the cockpit during the quiet cruise part of the flight; nine carried on as usual.
- The rest group slept on 93% of the rest opportunities.
- They fell asleep in 5.6 minutes and slept 25.8 minutes on average.
- Compared with the no-rest group, they showed better physiological alertness and performance, and the benefit lasted through descent and landing.
You will often see the study quoted as “34% better performance and 54% more alertness”. Those percentages do not appear in the report’s summary, so we give the numbers it does report. The takeaway still holds: a short, planned nap with a set wake-up time helped tired people stay alert.
Sleep inertia: why you can wake up groggy
The heavy, slow feeling right after waking is called sleep inertia. It fades the longer you are awake, and it is usually worse after longer naps, when you wake from deeper sleep, and when you were short of sleep to begin with. Keep naps to about 20 minutes, or allow a full 90, and give yourself time to wake up fully before you drive or do anything that could be dangerous.
When is it too late to nap?
Nap in the early afternoon, around the natural post-lunch dip, and finish at least 8 hours before bedtime. For most people that means before about 3 p.m. Late naps can make it harder to fall asleep at night. The calculator checks this against your own bedtime: for a 10:30 p.m. bedtime, a 20-minute nap with 5 minutes to fall asleep should start by 2:05 p.m.
Who should skip naps
- People with trouble sleeping at night. Relying on daytime naps can go with broken night sleep and insomnia. If nights are hard, skip naps or keep them short and early.
- Anyone using naps instead of night sleep. Naps help on the odd short night; they do not replace a full night. The sleep calculator helps you plan enough sleep, and how to fix your sleep schedule helps you move it.
- Babies and young children need naps as part of their daily sleep; this calculator is for teens and adults. For evenings with kids, make a bedtime routine chart.
If you need a nap every day even after a full night, fall asleep without meaning to, or snore loudly and feel tired all day, talk to a doctor. This calculator is a planning tool, not medical advice.
Frequently asked questions
How long should a power nap be?
About 10 to 20 minutes of sleep. In a sleep lab study, 10 minutes gave an immediate lift after a short night and 20 minutes helped a little later; 30 minutes left people groggy at first. Set the alarm for the nap plus the few minutes you need to fall asleep.
Is a 90-minute nap better than a 20-minute nap?
It does a different job. A 90-minute nap gives time for a full cycle of light, deep and REM sleep, which can help after a very short night, but it takes a big bite out of the afternoon and is harder to fit 8 hours before bedtime. For alertness on a normal day, 20 minutes is usually enough.
What time should I nap?
In the early afternoon, when many people feel a natural dip, and at least 8 hours before bedtime. For a 10:30 p.m. bedtime, a 20-minute nap with 5 minutes to fall asleep should start by about 2:05 p.m. The calculator warns you when a nap ends too close to your bedtime.
Why do I feel worse after a nap?
That groggy, slow feeling is sleep inertia. It is more likely after longer naps, when you wake from deeper sleep, and it fades the longer you are awake. Keep naps to about 20 minutes or allow a full 90, and give yourself time before driving.
What is the NASA nap?
In a 1994 NASA study, long-haul pilots were given a planned 40-minute rest in the cockpit. They fell asleep in about 6 minutes and slept about 26 minutes, and were more alert and performed better than pilots without the rest, right through descent and landing.
How long does it take to fall asleep for a nap?
It varies from person to person and day to day. The calculator assumes 5 minutes; change it to what is true for you. The NASA pilots, who were short of sleep, took 5.6 minutes on average.
Who should not nap?
If you have trouble sleeping at night, daytime naps can make it harder, so skip them or keep them short and early. Naps do not replace night sleep. If you need a nap every day even after a full night, or you fall asleep without meaning to, talk to a doctor.
Is this nap calculator for babies or kids?
No. It is for teens and adults. Babies and young children need naps as part of their daily sleep; see how much sleep each age needs on the sleep calculator, and use the bedtime routine chart for evenings.
Sources and evidence
- Brooks and Lack (2006): Which nap duration is most recuperative? — After a short night, a 10-minute afternoon nap improved alertness and performance at once; a 20-minute nap helped from about 35 minutes after waking; a 30-minute nap caused grogginess first, then helped.
- Rosekind et al. (1994): Crew factors in flight operations IX, effects of planned cockpit rest (NASA Technical Memorandum 108839) — 21 long-haul pilots; the 12 given a planned 40-minute rest slept on 93% of opportunities, fell asleep in 5.6 minutes and slept 25.8 minutes, with better physiological alertness and performance than the no-rest group through descent and landing.
- Hilditch and McHill (2019): Sleep inertia, current insights — Grogginess and slower thinking right after waking (sleep inertia) fade as time awake increases.
- Sleep Foundation: Napping, benefits and tips — About 20 minutes and no longer than 30 for alertness, or about 90 minutes for a full cycle; the early-afternoon dip; nap eight or more hours before bedtime, usually before 3 p.m.; relying on naps can go with fragmented night sleep or insomnia.
- Sleep Health Foundation: Napping — Short naps of 15 to 30 minutes in the early afternoon; late naps make it harder to sleep at night; take time to wake up fully before anything that could be dangerous; naps do not replace night sleep.