Last updated: September 2026
The siesta cultures had it right all along, with conditions attached. A nap can leave you sharper, brighter and more productive for the whole afternoon, or groggy and wide awake at midnight, and the difference comes down to two numbers: how long you sleep and what time you start.
Quick answer: Yes, naps are good for you when they are short and early: a 20 to 30 minute nap before about 3 pm measurably improves alertness and performance, and in NASA's famous study of pilots a 26-minute nap improved performance by around 34% and alertness by around 54%. Longer naps drop you into deep sleep and wake you groggy, and later naps drain the sleep pressure your night runs on. Naps cannot repay a chronic sleep shortage, and regularly needing long daytime sleeps despite full nights is worth mentioning to a GP.
Are naps good for you?
Short ones, genuinely. The best-known evidence is NASA's study of long-haul pilots, in which a planned cockpit nap averaging 26 minutes improved performance by around a third and alertness by around half, findings that turned strategic napping into standard practice in aviation. For the rest of us the payoff is the same in miniature: a short nap restores alertness, mood and concentration for the remainder of the day, without touching the night ahead.
The cautions sit at the edges. Napping long, napping late, or needing to nap every day regardless of how you slept are the versions that cause trouble, and each has a fix below.
How long should a nap be?
Twenty to thirty minutes, with an alarm set. That is long enough to bank the restorative light sleep and short enough to wake before deep, slow-wave sleep begins, which is the stage that produces the heavy, disoriented feeling on waking known as sleep inertia; we cover that mechanism in our guide to waking without grogginess. The worst nap length is the 45 to 60 minute middle ground, deep enough to hurt and too short to finish.
The one longer option that works is a full 90-minute cycle, which lets you pass through deep sleep and surface naturally from light sleep at the end. Save it for genuinely wrecked days, because 90 minutes of daytime sleep will be felt at bedtime.
When is the best time to nap?
Early afternoon, roughly 1 to 3 pm. Your body clock builds in a dip in alertness after lunch, so a nap there works with the rhythm rather than against it; if you work shifts, the equivalent window is about six to eight hours after waking. Our body clock guide explains the rhythm behind the dip.
After about 3 pm the trade turns bad: a late nap releases the sleep pressure that was building towards bedtime, and the night pays for the afternoon. If you are fighting to stay awake at 5 pm, a walk, daylight and an earlier bedtime beat a nap.
What is a coffee nap?
A real trick, oddly enough. Caffeine takes around 20 to 30 minutes to reach the brain, so drinking a coffee immediately before a 20-minute nap means the caffeine arrives just as you wake, stacking the nap's alertness on the coffee's. It works best before the mid-afternoon, for the same reason as any caffeine: too late in the day and it is still blocking sleep pressure at bedtime.
When are naps a bad sign?
When they stop being a choice. Needing a long nap every day despite seven to nine hours in bed suggests the night is not doing its job, and the usual suspects are poor sleep quality, an underlying issue such as sleep apnoea or low mood, or a mattress delivering broken sleep; persistent, unrefreshing long sleep is a GP conversation. Naps also cannot repay a chronic shortage, as our sleep debt guide explains; they patch the afternoon, but only earlier bedtimes repay the debt.
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Napping FAQs
Last updated: September 2026
Is a 2 hour nap too long?
For most people, yes. Two hours of daytime sleep drains the pressure your night runs on and often ends mid-cycle in grogginess. If you genuinely need two-hour naps despite full nights, treat it as a signal about the night's quality rather than a napping preference, and mention it to a GP if it persists.
What is the best nap length?
Twenty to thirty minutes with an alarm: NASA's pilot study found a 26-minute nap improved performance by around 34% and alertness by around 54%. If you have the time and the need, a full 90-minute cycle also works; the 45 to 60 minute middle is the worst option.
Why do I feel worse after a nap?
You slept past the light stages into deep, slow-wave sleep and woke mid-cycle, which causes sleep inertia, the heavy grogginess that can last an hour. Keep naps to 20 to 30 minutes with an alarm, or commit to a full 90 minutes, and nap before 3 pm.
Do naps count towards your sleep?
They restore alertness but do not substitute for the night: deep sleep and REM do their most important work in consolidated overnight sleep, and chronic shortfalls need earlier bedtimes rather than daytime patches. Think of naps as a supplement, not a payment plan.
Sources: Rosekind et al., Crew factors in flight operations: planned cockpit rest, NASA Technical Memorandum; Sleep Foundation, Napping.
