Results are estimates for healthy adults unless stated, and are not medical advice. Your doctor or a registered dietitian can give advice for your situation.
The length of a nap decides how you feel when you wake up. A short power nap can leave you sharper, while waking in the middle of deep sleep can leave you groggy for half an hour. This nap calculator tells you when to set your alarm for the two nap lengths that work best.
How to use the nap calculator
- Enter the time you plan to lie down.
- Choose roughly how long it takes you to fall asleep.
- Set your alarm for the power nap or full-cycle time shown.
Power nap vs full-cycle nap
Sleep moves through light sleep, deep sleep and REM sleep in cycles of about 90 minutes. A power nap of 10–20 minutes keeps you in light sleep, so you wake easily and feel more alert. A 90-minute nap lets you finish a whole cycle, including deep and REM sleep, and wake as it ends. It is useful after a short night, but needs more time.
Naps of about 30–60 minutes are the ones most likely to backfire. By then you are usually in deep sleep, and waking from it causes sleep inertia: grogginess that can last up to 30 minutes.
Example
If you lie down at 1:30 PM and take about 10 minutes to fall asleep, set your alarm for 2:00 PM for a power nap, or 3:10 PM for a full cycle. Try not to wake between about 2:10 and 2:40 PM.
Frequently asked questions
What is the best time of day to nap?
Early afternoon, roughly 1–3 PM, suits most people because alertness naturally dips after lunch. Late-afternoon and evening naps can make it harder to fall asleep at night.
Is napping every day bad for you?
Short daytime naps are fine for most healthy adults. If you need long naps every day despite sleeping enough at night, mention it to a doctor, as it can be a sign of a sleep problem.
Does a coffee nap work?
Some people drink a coffee just before a 20-minute nap, because caffeine takes about 20 minutes to kick in. It can help with alertness, but avoid it in the afternoon if caffeine affects your night-time sleep.
Sources
- National Sleep Foundation – guidance on napping
- Sleep Foundation / American Academy of Sleep Medicine – sleep stages and sleep inertia