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Nap planner: how long to nap and when to set the alarm
One alarm time for the nap you have room for, timed so deep sleep doesn't leave you groggy. You also get the latest start that keeps tonight's bedtime clear.
If you lie down at 2:00 PM
ChangeThe dotted line is time to fall asleep. The dip is the nap.
Why this time?
Nap planner: Change the nap
Nap goal
10 to 240 minutes, from lying down to getting up.
4 more settingsWoke at 7:00 AM
0 to 45. We start at 15 (studio rule).
Studio rule, checked against when the nap ends.
Night-shift naps
A 2:35 PM alarm, and something to nap to.
The Lull app plans naps like this one, coffee naps too, and can play a fan or rain sound that stops before your phone's alarm.
See the Lull appLying down at 2:00 PM for a 20-minute nap? Allow 15 minutes to fall asleep and set the alarm for 2:35 PM.
When to set the nap alarm
Alarm times for each goal from three lie-down times, allowing the planner's 15 minutes to fall asleep and room for the whole nap:
| Lying down at | Quick boost (20 min) | A little more (30 min) | Full cycle (90 min) |
|---|---|---|---|
| 1:00 PM | 1:35 PM | 1:45 PM | 2:45 PM |
| 2:00 PM | 2:35 PM | 2:45 PM | 3:45 PM |
| 3:00 PM | 3:35 PM | 3:45 PM | 4:45 PM |
When a nap time is wrong for you
The planner cannot know how fast you fall asleep today, how tired you are, or how a nap affects your own night. The 15 minutes to fall asleep and the no-nap window before bed are our rules of thumb, not published figures, and you can change both. The nap lengths come from NIOSH and the CDC Yellow Book, but a nap that ends on time for the arithmetic can still leave some grogginess.
See a doctor if you are sleepy every day whatever you do, need naps just to get through the day, or regularly take more than 30 minutes to fall asleep at night (NIOSH lists that among the symptoms to raise with a health care provider). This page is general information, not medical advice: read our disclaimer.
How the nap planner works
The alarm time is plain arithmetic: the time you lie down, plus the minutes you expect to need to fall asleep, plus the nap itself. The planner starts from the nap you asked for: 20 minutes for a quick boost, 30 minutes for a little more, or 90 minutes for a full sleep cycle. If the time you have will not hold it, it does not stretch into the middle ground between 30 and 90 minutes; it steps down to 30 minutes or less. With less than 10 minutes of sleep left, it says there is not enough time.
Two checks come with the alarm. The first is how long you have been awake when you lie down, which catches a mistyped time. The second is tonight's bedtime: the planner looks at when the nap ends, not when it starts, and warns if that is inside your no-nap window. It also gives the latest time you could lie down for a nap of this length and still clear the window.
Worked example: an afternoon nap
You woke at 7:00 AM, want a quick boost, lie down at 2:00 PM, go to bed at 11:00 PM and have 60 minutes. With 15 minutes to fall asleep and 20 min of sleep, the alarm is 2:35 PM. You have been awake 7 h. With the usual 6-hour window, the latest time to lie down is 4:25 PM, so 2:00 PM is clear. Choose the full cycle instead in the same hour and 1 h 45 min does not fit, so the planner gives 30 min of sleep and an alarm at 2:45 PM, and says it shortened the nap. With two hours to spare the full cycle fits: alarm at 3:45 PM.
Reading the alarm, the strip and the boxes
The large time is the alarm, and the strip under it draws the time to fall asleep and the nap to scale. The boxes give the time lying down, the hours since you woke and the latest start that clears tonight's window. Each line under them links its figure to the methodology page.
The values behind this alarm time
Each row is one value this tool uses, with its tier: Primary = read off the source page, Secondary = reported by the source from another body, Studio rule = our own choice, with the reason given on the methodology page. The links in the result above go to the same rows there.
Quotes, notes and the date we last read each source are on the methodology and sources page.
Which nap length, and why these three
NIOSH's training for nurses says that waking from a nap at 20 minutes, before going into deeper sleep, or at about 90 minutes, the predicted end of a sleep cycle, may leave less grogginess on waking. The CDC Yellow Book describes short daytime naps of 20 to 30 minutes to help stay alert during the day. Those give the three goals. A cycle of about 90 minutes also sits inside the 80 to 100 minute range the NHLBI gives for a sleep cycle, which is why it is the one long option.
Research on the shortest naps points the same way. In a small study, Brooks and Lack (2006) gave young adults who had slept about five hours an afternoon nap of different lengths and reported that the 10-minute nap was overall the most effective of the lengths they tried. It is one study of one group, so it is not one of the goals here. It is still why the planner will plan a nap as short as 10 minutes when time is tight.
Grogginess after a nap
The heavy, slow feeling after waking is called sleep inertia. NIOSH's training for nurses says that research indicates it typically lasts 30 to 60 minutes, and that researchers have observed it lasting 2 hours. After a nap of 20 minutes or about 90 minutes, the same training says grogginess may go away more quickly, within 15 to 30 minutes, because you are likely to wake from lighter sleep. It is worse when you wake from deeper sleep, which is why the length matters more than the exact minute you lie down. NIOSH also reports that bright light and washing the face helped people feel alert again sooner after a nap.
Caffeine and a short nap
Some people have a coffee just before a short nap. NIOSH describes this and notes that caffeine takes about 30 minutes to reach full effect, so it starts working around the time a short nap ends. Caffeine taken in the afternoon can still be active at bedtime, so the caffeine cut-off calculator is the place to check how late a coffee nap can go.
Naps and tonight's sleep
A nap late in the day can make it harder to fall asleep at night. There is no published cut-off, so the no-nap window is our own rule of thumb: 6 hours before bed by default, with 4 and 8 as the other choices. If naps never bother your night, the shorter window may suit you; the longer one is the other option. Night-shift workers sleep by different rules, which the night-shift sleep planner covers.
Questions about naps
How long should a nap be?
For a quick lift, a short nap: NIOSH points to 20 minutes, before deeper sleep, and the CDC Yellow Book describes 20 to 30 minutes. With more time, about 90 minutes, the end of a sleep cycle. The planner avoids the lengths in between.
Why is the alarm later than the nap length?
Because you do not fall asleep the moment you lie down. The planner adds 15 minutes by default (our rule of thumb; you can change it), so a 20 minute nap from 2:00 PM has an alarm at 2:35 PM.
What time is too late to nap?
No official body gives a cut-off. The planner uses our own rule of thumb, no nap ending in the last 6 hours before bed, and lets you pick 4 or 8 instead.
Why do I feel worse after a longer nap?
Waking from deeper sleep brings sleep inertia. NIOSH says it typically lasts 30 to 60 minutes and has been observed lasting 2 hours, while after a 20 minute or about 90 minute nap it may clear within 15 to 30 minutes. That is why the planner keeps to short naps or a whole cycle.
Does a coffee before a nap help?
NIOSH describes it: caffeine takes about 30 minutes to reach full effect, so it starts working as a short nap ends. Check the caffeine cut-off calculator before having one late in the day.
Can I plan my main night's sleep here?
No. For a night's sleep, the sleep calculator counts whole cycles back from your alarm. For daytime sleep after a night shift, use the night-shift sleep planner.
Is what I enter stored anywhere?
No. The alarm time is worked out in your browser. The share link holds only the times and choices in the form, and only if you copy it.
More questions about the site, its sources and privacy are answered in the Lull FAQ.