Nap calculator
Choose a power nap (10–20 minutes) or one full sleep cycle (about 90 minutes), enter when you’ll lie down, and get the time to set your alarm.
Nap alarm calculator
Set your alarm for
20-minute power nap starting at .
Short naps of about 20 minutes, and no longer than 30, are the usual advice for adults; waking from deep sleep can leave you groggy [1].
This calculator gives general estimates based on average 90-minute sleep cycles. It isn’t medical advice. If you have ongoing trouble sleeping, loud snoring, or daytime sleepiness, talk to a doctor.
How accurate is this? It’s a timing aid, not a prediction of your sleep stages. Cycles average about 90 minutes but vary between roughly 70 and 120 minutes [2], and naps don’t always follow the same pattern as night sleep.
Power nap or full-cycle nap?
| Feature | Power nap | Full-cycle nap |
|---|---|---|
| Length | 10–20 minutes (this calculator) | About 90 minutes (one cycle) |
| What the source says | About 20 minutes and no longer than 30 is the best nap length for most adults [1] | A nap of around an hour and a half may also be beneficial [1] |
| Grogginess risk | Lower: sleep inertia is less likely after naps of 30 minutes or less [3] | Aims to end after a full cycle, but a cycle can be shorter or longer than 90 minutes |
| Effect on tonight | Small if taken earlier in the day | A long nap late in the day may be problematic for night sleep [1] |
Why 20 minutes?
The Sleep Foundation explains that 20 minutes lets you get a bit of light sleep to boost alertness without entering deep sleep, and that waking up from deep sleep can cause grogginess and actually worsen sleepiness [1]. In one laboratory comparison described in a sleep inertia review, a 10-minute afternoon nap improved performance straight away, while after a 30-minute nap improvements took from 35 up to 95 minutes to appear, depending on the task [3].
Why 90 minutes?
A full cycle takes you through light sleep, deep sleep and REM sleep and back towards lighter sleep. Cycles average about 90 minutes [2], so a 90-minute nap aims to end near the end of one. If you wake up groggy after full-cycle naps, try a slightly shorter or longer cycle length in the calculator.
Avoid the 30–60 minute zone
Naps longer than about half an hour are more likely to reach deep sleep, which is why the usual advice is to keep a nap to around 20 minutes and no longer than 30 [1]. The calculator’s power-nap setting therefore stops at 20 minutes. If you need more than that, the full-cycle option is the alternative.
Timing your nap
Experts typically recommend that adults take naps eight or more hours before bedtime; for most people, that means before 3 p.m. [1]. Enter tonight’s bedtime in the calculator and it warns you if the nap ends less than 8 hours before it.
The early-afternoon slump many people notice after lunch is linked to the body’s circadian rhythm, according to the Sleep Foundation [1], which makes it a natural time for a short nap.
- Enter the time you’ll lie down, or press “Now”.
- Choose a power nap or a full cycle.
- Tick “Add time to fall asleep” if you usually take a while to drift off.
- Set your alarm for the time shown, and get up when it rings rather than snoozing [1].
Naps are a top-up, not a replacement
A nap can help on a day after a short night, but it doesn’t replace a full night: napping is not a substitute for high-quality nighttime sleep [4]. If you find you need a nap every day even after 7 or more hours in bed, feeling sleepy despite enough sleep can be a sign of poor sleep quality [5], and it’s worth discussing with a healthcare provider.
Related guides
See how sleep stages work and how much sleep you need each day.
- Sleep cycles explained: the stages, REM, and why cycles vary.
- How much sleep do you need by age?: the recommended hours for every age group.
- Sleep FAQ: 26 common questions, answered with sources.
Frequently asked questions
How long should a nap be?
For most adults, the Sleep Foundation says the best nap length is about 20 minutes and no longer than 30 minutes [1].
Is a 20-minute nap better than a 90-minute nap?
They do different jobs. A 20-minute nap gives a bit of light sleep without entering deep sleep, while a nap of around an hour and a half lets you go through a full cycle and may also be beneficial [1]. The longer nap takes more time and is more likely to affect your night if it’s late in the day.
Why do I feel worse after a 45-minute nap?
Longer naps can reach deep sleep, and waking from deep sleep can cause grogginess [1]. Research on sleep inertia notes that it is less likely after short naps of 30 minutes or less [3].
When is the best time to nap?
Experts typically recommend that adults nap eight or more hours before bedtime, which for most people means before 3 p.m. [1].
Should I include the time it takes to fall asleep?
If you usually take a while to drop off, tick “Add time to fall asleep” so the nap length counts from when you’re actually asleep. Leave it off if you nod off quickly.
Can napping replace sleep at night?
No. The Sleep Foundation says napping is not a substitute for high-quality nighttime sleep [4].
Is it normal to need a nap every day?
Feeling sleepy during the day despite enough sleep can be a sign of poor sleep quality [5]. If it happens regularly, talk to a healthcare provider.
Does coffee before a nap help?
A review of sleep inertia found that caffeine taken before a short nap (for example 20 minutes) has been shown to reduce grogginess afterwards [3]. Caffeine also stays in the body for hours (its half-life averages about 5 hours [6]), so a coffee nap late in the day can cost you night-time sleep.
Sources
- Sleep Foundation: Napping: Benefits and Tips. May 27, 2026. Accessed October 21, 2026.
- Sleep Foundation: Stages of Sleep: What Happens in a Normal Sleep Cycle?. July 25, 2025. Accessed October 21, 2026.
- Peer-reviewed review (open access): Sleep inertia: current insights (Hilditch & McHill, Nat Sci Sleep 2019;11:155–165). 2019. Accessed October 21, 2026.
- Sleep Foundation: Caffeine and Sleep. July 16, 2025. Accessed October 21, 2026.
- CDC: About Sleep. May 15, 2024. Accessed October 21, 2026.
- Peer-reviewed review (open access): Common questions and misconceptions about caffeine supplementation (Antonio et al., J Int Soc Sports Nutr 2024). 2024. Accessed October 21, 2026.
Last reviewed by the CycleRest team (sources re-checked; no medical reviewer). Editorial policy