Nap Calculator: How Long to Nap and When to Wake
A nap calculator tells you when to set your alarm so a nap helps rather than leaves you groggy. This guide explains how it works, shows example alarm times and covers when to nap.
Key takeaways
- For a quick boost, 10 to 20 minutes is the most practical nap length.
- Set your alarm for the nap length plus about 10 minutes to fall asleep.
- Nap before mid-afternoon so it does not delay your bedtime.
- A 90-minute nap can complete a cycle and may feel less groggy than 30 to 60 minutes.
How a nap calculator works
Alarm time = nap start + time to fall asleep + nap length.
Most people take 5 to 15 minutes to fall asleep during the day, so 10 minutes is a sensible default. Enter your start time into the nap calculator to see alarm times for short and long naps.
Nap alarm times by start time
| Lie down at | 20-minute nap | 30-minute nap | 90-minute nap |
|---|---|---|---|
| 1:00 PM | 1:30 PM | 1:40 PM | 2:40 PM |
| 2:00 PM | 2:30 PM | 2:40 PM | 3:40 PM |
Includes 10 minutes to fall asleep.
Choosing a nap length
- 10 to 20 minutes: a quick alertness boost with little grogginess.
- 30 minutes: can leave some people groggy on waking.
- 60 minutes: more deep sleep, but a higher chance of grogginess.
- 90 minutes: a full cycle, often easier to wake from.
Read more in our napping guide.
When to nap
Most people feel a dip in the early afternoon, so a nap between about 1 PM and 3 PM fits the body’s rhythm. Later naps can make it harder to fall asleep at night. If you have insomnia, keep naps short or skip them.
The coffee nap
Some people drink a cup of coffee and then nap for 15 to 20 minutes, waking as the caffeine begins to work. It can help, but caffeine late in the day may disrupt night sleep. See caffeine and sleep.
Frequently asked questions
How long should a power nap be?
About 10 to 20 minutes for most adults.
Why do I feel worse after napping?
You may have woken from deep sleep. Try 20 minutes or a full 90 minutes.
Sources and further reading: American Academy of Sleep Medicine (aasm.org), Sleep Research Society, National Sleep Foundation (sleepfoundation.org), CDC sleep resources (cdc.gov/sleep). See our full source list and editorial policy. This guide is general information, not medical advice.