How long should a nap be?

For most people a 10–20 minute power nap is ideal: it restores alertness without sliding into deep sleep. If you have more time, a full 90-minute sleep cycle lets you wake from light sleep and feel refreshed. Avoid the 30–60 minute middle ground if you need to be sharp straight away.

Why is a 20-minute nap ideal?

A 20-minute nap keeps you in the lighter stages of sleep, so you wake easily and get a quick boost in alertness and mood without the grogginess that comes from being woken out of deep sleep.

Is a 30-minute nap bad?

Not bad, but a 30–60 minute nap is the most likely to leave you groggy, because the alarm tends to interrupt deep slow-wave sleep. If you only have half an hour, capping the nap nearer 20 minutes usually feels better.

What time of day is best to nap?

Early afternoon — roughly between 1 and 3 PM — lines up with the natural post-lunch dip in alertness. Napping too late in the day can make it harder to fall asleep at night.

Why do I wake up groggy from naps?

That heavy, foggy feeling is sleep inertia. It happens when an alarm pulls you out of deep sleep mid-cycle. Keeping a nap to about 20 minutes, or extending it to a full 90-minute cycle, both help you wake from lighter sleep instead.

Nap Calculator

This nap calculator finds the ideal nap length and the time to set your alarm — a quick power nap, a longer recovery nap, or a full sleep cycle — adding a 15-minute buffer for the time it takes to drift off.

How it works

Sleep moves through stages: light sleep, then deep slow-wave sleep, then REM, in cycles of roughly 90 minutes. Waking from light sleep feels easy; waking out of deep sleep leaves you groggy. A nap works best when your alarm lands in light sleep — either before you reach deep sleep (a short power nap) or after a whole cycle completes.

The calculator takes the time you lie down, adds about 15 minutes to fall asleep, then adds the nap length, and shows the resulting wake time for each nap type: wake time = start + 15 min + nap length.

Worked example

You lie down for a nap at 2:00 PM. Allowing 15 minutes to fall asleep, a 20-minute power nap means setting your alarm for 2:35 PM (2:00 + 15 + 20). If instead you want a full 90-minute sleep cycle, set the alarm for 3:45 PM (2:00 + 15 + 90).

Nap types at a glance

Nap type	Length	Best for
Power nap	20 min	Quick alertness, no grogginess
Recovery nap	60 min	Memory & learning (may wake groggy)
Full cycle	90 min	Full sleep cycle, easier wake, creativity

Frequently asked questions

How long should a nap be?: For most people a 10–20 minute power nap is ideal: it restores alertness without sliding into deep sleep. If you have more time, a full 90-minute sleep cycle lets you wake from light sleep and feel refreshed. Avoid the 30–60 minute middle ground if you need to be sharp straight away.
Why is a 20-minute nap ideal?: A 20-minute nap keeps you in the lighter stages of sleep, so you wake easily and get a quick boost in alertness and mood without the grogginess that comes from being woken out of deep sleep.
Is a 30-minute nap bad?: Not bad, but a 30–60 minute nap is the most likely to leave you groggy, because the alarm tends to interrupt deep slow-wave sleep. If you only have half an hour, capping the nap nearer 20 minutes usually feels better.
What time of day is best to nap?: Early afternoon — roughly between 1 and 3 PM — lines up with the natural post-lunch dip in alertness. Napping too late in the day can make it harder to fall asleep at night.
Why do I wake up groggy from naps?: That heavy, foggy feeling is sleep inertia. It happens when an alarm pulls you out of deep sleep mid-cycle. Keeping a nap to about 20 minutes, or extending it to a full 90-minute cycle, both help you wake from lighter sleep instead.

Related calculators

Disclaimer. This is general guidance for healthy adults; ideal nap length and sleep needs vary from person to person and with age, schedule, and health. It is not medical advice — talk to a clinician about persistent daytime sleepiness or sleep problems.