Naps
How long a nap should be, and why thirty minutes is the wrong answer
Nap advice usually arrives as a single number with no mechanism attached, which is why it fails the moment your day does not match the assumption behind it. There are three facts underneath all of this, and once you have them the right length for any given afternoon is obvious.
In short
For alertness, nap for 20 minutes: long enough to help, short enough to end before slow wave sleep. For recovery, nap for 90 minutes, which is roughly one full cycle and brings you back to a lighter stage before the alarm. Avoid 30 to 60 minutes, which is long enough to reach deep sleep and too short to get through it.
- For alertness
- 20 minFor alertnessEnds before deep sleep
- For recovery
- 90 minFor recoveryOne complete cycle
- The one to avoid
- 30 minThe one to avoidDeep sleep, no exit
Three facts, and every nap recommendation follows from them
The first is that sleep inertia, the heavy disoriented feeling after waking, is a stage effect rather than a duration effect. It is mild when you surface from light sleep and severe when you are pulled out of slow wave sleep, and that difference is larger than any difference caused by how long you slept.
The second is that most people reach slow wave sleep somewhere after about twenty five minutes, and sooner than that when they are already short on sleep. That single number is why the standard advice is twenty minutes: it is the largest nap that reliably stops before the cliff.
The third is that a full cycle runs roughly ninety minutes and ends near the surface again. That is why the other recommended length is ninety rather than sixty, and why sixty is a worse nap than either of its neighbours despite sitting neatly between them.
Put those together and the shape of the advice is not arbitrary at all. Stay short enough to miss the deep stages, or go long enough to come out the far side of them. The middle is the only genuinely bad option, and it is the one most people default to.
Every length, with both sides stated
Each of these pages says what the length buys and what it costs, at the same size, because a nap page that only lists benefits is how people end up taking the thirty minute one.
- The 10 minute napA 10 minute nap lifts alertness without taking you into slow wave sleep, so you wake up clear rather than groggy. It is the safest nap to take close to work or driving, and it does nothing for memory consolidation, which needs considerably longer.
- The 20 minute napA 20 minute nap is the standard recommendation because it produces a solid alertness benefit while ending before most people reach slow wave sleep, so you wake up clear rather than groggy. It is long enough to be worth the time and short enough to stay safe.
- The 30 minute napA 30 minute nap frequently ends inside slow wave sleep, which produces the strongest sleep inertia of any nap length. That is the heavy, disoriented feeling that can take twenty minutes or more to clear, and it is why 20 minutes or a full 90 minute cycle are both better choices.
- The 60 minute napA 60 minute nap includes a substantial amount of slow wave sleep, which is useful for recovery and for some kinds of memory, and it usually ends before the cycle completes. That means the benefit is real and the wake-up is often groggy, so it suits situations where the hour afterwards is flexible.
- The 90 minute napA 90 minute nap is approximately one full sleep cycle, which means it ends in a lighter stage rather than in slow wave sleep. That produces much less grogginess than a 30 or 60 minute nap, and it includes both the deep sleep and the REM that shorter naps miss.
- The coffee napA coffee nap means drinking caffeine and then immediately napping for about 20 minutes. Caffeine takes roughly 20 to 30 minutes to have a noticeable effect, so it does not stop you falling asleep quickly, and you wake as it takes hold. The two effects add rather than cancel.
Where the arithmetic runs out
Every number on this page is an average standing in for something variable. Twenty five minutes to slow wave sleep is a typical figure, not yours, and it moves with how much sleep you are carrying: arrive at a nap after five hours of sleep and the deep stages come sooner than the advice assumes. Ninety minutes for a cycle is likewise a mean, with real ones running roughly seventy to a hundred and twenty.
Which means a timer is always guessing. It knows how long it has been counting and nothing about what your brain is doing, so the advice on this page is the best available guess rather than a rule. That is the same limitation a bedtime calculator has, and the same onesmart wake exists to work around on a night alarm: watch the window for a lighter moment and ring on it, rather than trusting a number that was only ever a population average.
If your naps are getting longer and more necessary rather than shorter and optional, that is a pattern worth raising with a doctor rather than optimising with a timer. Nothing on this site is medical advice and Tock is not a medical device.
Questions people ask
How long should a nap be?
Twenty minutes if you want to feel sharper for the rest of the afternoon, because that ends before most people reach slow wave sleep. Ninety minutes if you are recovering from a short night, because that is roughly one full cycle and brings you back up before the alarm. Thirty to sixty minutes is the range to avoid.
Why do I feel worse after a nap?
Because you were probably woken out of slow wave sleep, which produces the strongest form of sleep inertia. It is about which stage you were in rather than how long you slept, and it can take twenty minutes or more to clear. Naps between about thirty and sixty minutes are the most likely to do it.
Do naps affect sleep at night?
Yes, in proportion to their length and how late they are. A nap discharges sleep pressure, and whatever it discharges is not available at bedtime. Ten or twenty minutes early in the afternoon has little effect. Ninety minutes at five in the evening reliably pushes your bedtime later.
Is napping bad for you?
Not inherently. A short early afternoon nap is a normal part of many peoples day and there is nothing wrong with it. What is worth attention is a sudden need for long daily naps that was not there before, which is a change worth mentioning to a doctor rather than solving with a timer.
Elsewhere on the site
A different corner of the same problem.
- Wake tonesGentle alarm soundsA gentle alarm works when it catches you at a light moment and fails when it lands in the heaviest part of your night, which is a timing problem rather than a volume one. Tock watches movement and sound across the 30 minutes before your alarm and rings early at a lighter moment if it finds one, with your set time as the fallback.
- Head to headSleepScore vs SnoreLabIf snoring is the complaint and you want to find out whether the mouthguard made a difference, SnoreLab. If you want the whole night measured without wearing anything, SleepScore.
- FeaturesSleep scoreThe sleep score is a single number for a night, sitting at the top of that night detail view. Underneath it are the parts that produced it, and across nights the insights cover 21 metrics in 7 groups plus long-run measures like sleep regularity and sleep debt.
- Sleep soundsDistant stormFar-off thunder helps at the start of the night because the slow rolling swells give your attention something easy to follow while it lets go, and it hurts later because every roll is a change in level, which is exactly what surfaces a light sleeper. Tock treats it as a fall-asleep aid and fades it out after half an hour by default.
- Tock for youNew parentsYou do not wake up to an alarm any more, you wake up to a small person, three or four times, and then you have to be a functioning adult by seven. The night is not so much short as it is in pieces.
- AlternativesTock vs RiseChoose Rise if planning your day around energy peaks and a running sleep debt is what actually changes your behaviour. Choose Tock if you want the alarm itself to be smarter, the night recorded from the phone, and a coach that can talk about what it heard.
The clock does not know what stage you are in
Whether twenty minutes ends before deep sleep depends on how fast you dropped off and how short last night was. Tock watches for a lighter moment inside the window instead of counting to a number.