Nap Calculator
Find the alarm time for a 20-minute power nap or a 90-minute full-cycle nap, or the time to lie down to be up on time.
Result
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The nap calculator tells you when to set the alarm for a 20-minute power nap or a full 90-minute sleep cycle, based on when you lie down and how long you take to fall asleep. You can also work backwards from the time you need to be up.
Examples
Lying down at 1:30 PM
With 10 minutes to fall asleep, a 20-minute nap alarm is at 2:00 PM and a 90-minute nap alarm is at 3:10 PM.
Must be up by 4:00 PM
With 10 minutes to fall asleep, lie down at 3:30 PM for a 20-minute nap, or at 2:20 PM for a 90-minute nap.
Falls asleep instantly, lying down at 4:00 PM
With 0 minutes to fall asleep, a 20-minute nap ends at 4:20 PM and a 90-minute nap at 5:30 PM. A nap this late in the day can make it harder to fall asleep that night.
Nap alarm times by lie-down time (10 minutes to fall asleep)
| Lie down at | 20-minute nap alarm | 90-minute nap alarm |
|---|---|---|
| 12:00 PM | 12:30 PM | 1:40 PM |
| 1:00 PM | 1:30 PM | 2:40 PM |
| 2:00 PM | 2:30 PM | 3:40 PM |
| 3:00 PM | 3:30 PM | 4:40 PM |
Frequently Asked Questions
How long should a nap be?
For a quick boost, the Cleveland Clinic describes power naps as about 10 to 30 minutes, and the Sleep Foundation says naps under 20 minutes improve alertness with little or no grogginess. If you have time, a nap of about 90 minutes can run through a full sleep cycle, though the Cleveland Clinic notes that waking after a whole cycle can still leave you groggy. This calculator offers 20 minutes and 90 minutes.
Why avoid a 30 to 60 minute nap?
A longer nap is more likely to reach deep sleep, and waking from deep sleep can leave you groggy for a while, a state called sleep inertia. The Cleveland Clinic notes that longer naps have the downside of more sleep inertia. Ending a nap before deep sleep reduces the chance.
What is the best time of day to nap?
The Sleep Foundation says naps in the early or mid-afternoon are unlikely to interfere with nighttime sleep. A late nap can make it harder to fall asleep at night, so the calculator adds a reminder when the nap starts at 4 PM or later.
Does the nap length include the time to fall asleep?
No. The alarm time adds your fall-asleep time on top of the nap length, so a 20-minute nap with a 10-minute fall-asleep time puts the alarm 30 minutes after you lie down. Set the fall-asleep field to 0 if you want the alarm exactly one nap length after you lie down.
Is a 90-minute nap better than a 20-minute nap?
They do different jobs. A 20-minute nap is quick and easy to fit in. A 90-minute nap takes much more time but ends at the end of a cycle, which avoids waking you in the middle of deep sleep, although some people still wake groggy. Choose the one that fits your day.
Related Information
Related sleep tools
- Sleep calculators and guides - every sleep calculator and bedtime guide in one place.
- Sleep Cycle Calculator - Bedtimes and wake-up times from 90-minute sleep cycles.
- Sleep Debt Calculator - How many hours short of your target the last week left you.
- Sleep Efficiency Calculator - The share of your time in bed that you spent asleep.
Key Terms
- Power nap
- A short nap, usually 10 to 30 minutes, taken for alertness.
- Sleep inertia
- The groggy, disoriented feeling just after waking, strongest after waking from deep sleep.
- Sleep cycle
- One pass through non-REM and REM sleep, about 90 minutes on average.
Sources
- Cleveland Clinic: Power Naps: Benefits and How To Do It — Cleveland Clinic
- Sleep Foundation: Do Power Naps Work? — Sleep Foundation
Result
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Quick Tips
- •Short naps of about 10 to 30 minutes are the usual advice for a quick boost; under 20 minutes gives alertness with little or no grogginess.
- •Nap in the early or mid-afternoon. Napping late in the day can interfere with sleep at night.
- •Allow a few minutes after waking before anything that needs full attention, since grogginess can linger.
- •Set the alarm and put the phone out of reach so the nap does not run on.