Nap Calculator

What the nap calculator does

Tell the calculator what time you want to lie down and it shows when to set the alarm for the nap length that fits your day. A nap of 10 to 20 minutes is meant to sharpen alertness without dropping into deep sleep. A nap of about 90 minutes can complete one full sleep cycle. Anything in between risks waking from slow wave sleep and feeling groggy.

When to nap

Most people have a natural dip in alertness in the early afternoon, around 1 to 3 PM, which is a good window. A nap after about 4 PM can make it harder to fall asleep at night for some people, because it reduces sleep pressure, the drive built by adenosine during waking hours.

A worked example: you lie down at 1:30 PM and fall asleep in about 10 minutes. For a 20 minute nap set the alarm for 1:50 PM, which is 20 minutes after you fall asleep, so about 2:00 PM when counting from lying down. For a 90 minute cycle nap set it for 3:10 PM.

Pick the exact length with the pages for a 20 minute nap, a 30 minute nap and a 90 minute nap.

How to nap well

1. Choose a dim, cool, quiet room, or use an eye mask.
2. Set the alarm before you lie down so you are not watching the clock.
3. Drink water and avoid a heavy meal just before.
4. Give yourself 15 to 30 minutes after waking before hard tasks, because sleep inertia can linger.
5. Keep naps before about 3 or 4 PM, and keep them out of the night plan.

Some people find a coffee right before a 20 minute nap works because caffeine takes around 20 to 30 minutes to start acting. It is not suitable for everyone, especially if you are sensitive, so check the caffeine sleep calculator.

Who should be careful with naps

If you have trouble falling asleep at night, daytime naps may be working against you. Try a week with no naps and fix the night first using the bedtime calculator. If you need long naps every day despite 7 or more hours at night, speak to a doctor, because that can be a sign of a sleep problem.

• Teens and students: a short nap before homework can help, a long late nap can push bedtime later.
• Shift workers: a planned nap before a night shift is a common tool, see shift work sleep.
• Ramadan: a short afternoon nap helps bridge a split sleep pattern, see napping between Dhuhr and Asr.
• Older adults: short naps are common, keep them brief and early.

Related tools

To understand what happens inside a nap read the best nap length and what sleep inertia is. For the night side, try the wake up calculator or open the sleep calculator hub.

Nap planner by goal

Times are guides. Match the nap to your real day: early afternoon naps protect your night better than late ones.

Nap rules worth following

• Do not nap within about 6 hours of your normal bedtime if you struggle to fall asleep.
• Stay under 30 minutes unless you can afford a full 90 minutes.
• Treat a daily need for long naps as a signal to check your nights with the sleep hours calculator.
• After Fajr, a short rest of 10 to 20 minutes can be used in Ramadan, see sleep in Ramadan.

The 10 minute, 45 minute and 60 minute pages each have a full schedule.

Key terms explained

• Power nap: a short nap, usually 10 to 20 minutes.
• Sleep inertia: grogginess after waking.
• Sleep pressure: the urge to sleep that naps reduce.
• Siesta: a midday rest common in warm regions.
• Slow wave sleep: deep sleep that appears in longer naps.

See more in the sleep glossary.

Myths and facts about sleep timing

• Myth: 90 minutes is exact. Fact: it is an average. Cycle length differs between people and can change through the night.
• Myth: you can train yourself to need five hours. Fact: a few people have a true short sleep need, but they are rare. Most people who believe they do well on less show slower reaction times when tested, as the 2003 Van Dongen study of chronic sleep restriction found.
• Myth: weekend lie ins fix a weak week. Fact: a long sleep in offers partial relief and can push your clock later. See can you catch up on sleep.
• Myth: a nightcap helps sleep. Fact: alcohol may help you fall asleep faster but tends to fragment sleep and reduce REM in the second half of the night.
• Myth: the bedroom should be warm and cosy. Fact: a cool room, about 15 to 19 degrees Celsius (60 to 67 F), is the common guideline.

Napping across regions

Readers in Pakistan, India, the UAE, the UK, the US, Canada and Australia use the same sleep science but live very different days. See the local guides for Pakistan, India, the UAE, the UK, the USA, Canada and Australia, or browse sleep guides by city for local sunrise and climate tips.

Five real nap situations and what to do

You feel a slump at 2 PM

Lie down at 1:45 PM, set the alarm for 20 minutes after you expect to fall asleep, and aim to be up by about 2:10 PM. Short naps keep you in light sleep, so you usually wake quickly. Drink water and step into daylight afterward.

You slept five hours last night

A 90 minute nap in the early afternoon can complete one full cycle and help with mood and alertness. It will not repay the whole shortfall. Go to bed earlier tonight, using the bedtime calculator to choose the time.

You work a night shift

A nap of 60 to 90 minutes in the early evening before the shift builds some sleep pressure reserve. Keep the room dark and treat it as part of your sleep plan with the shift work sleep calculator.

You are fasting in Ramadan

Split sleep usually means a night block plus a daytime nap. A 20 to 30 minute rest after Dhuhr or a 90 minute nap in the afternoon can help. The Dhuhr to Asr nap guide gives timing ideas.

You are driving a long distance and feel drowsy

Pull over somewhere safe and take a 15 to 20 minute nap. Fresh air and loud music do not fix drowsiness. Drowsy driving is dangerous, so stop rather than push on.

How to read the result

The calculator gives you an alarm time for each nap type, counted from the moment you expect to fall asleep. If you usually need 10 minutes to fall asleep, add that to the nap. A 20 minute nap that begins at 1:30 PM therefore ends near 1:55 PM to 2:00 PM. If the result lands late in the day, choose the shorter nap or skip it.

• Short nap: the alarm is the key. Without it, a 20 minute nap can drift into 40 minutes and end in deep sleep.
• Full cycle nap: give yourself 90 minutes plus the time to fall asleep, so about 100 minutes in total.
• In between: if you wake groggy, the nap probably ended in deep sleep. Try 20 or 90 minutes next time.

What the science says about napping

Naps change two things: how much sleep pressure you carry, and how alert you feel right after. Sleep pressure is the drive to sleep that builds through the day because of adenosine, a chemical that accumulates while you are awake. A nap clears some of it. That is why it helps with alertness and why a late nap can make bedtime harder.

Short naps stay in the lighter NREM stages. Longer naps can include slow wave sleep, which brings sleep inertia on waking, and naps of about 90 minutes can cover a whole cycle with REM. The details differ from person to person, so the tool gives a range of options rather than one answer.

Nap mistakes to avoid

• Napping for 30 to 45 minutes and then getting up straight into a hard task. Sleep inertia can hit hardest here.
• Napping late in the evening and then wondering why you cannot sleep at night.
• Using naps to cover for chronic short nights without fixing the nights.
• Lying down with a bright phone. The light and content delay sleep onset.
• Skipping the alarm. Without it you cannot control what stage you wake in.

For the long form read the best nap length guide, and try the sleep hours calculator to see if nights are the real issue.