Nap Calculator
How long should you nap?
Some nap lengths leave you sharper; others leave you destroyed. Pick the duration that matches your goal, we'll tell you the wake time.
Time you'll lie down. Add a few minutes to fall asleep.
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Wake at,
A 10-minute nap delivers measurable alertness gains within the first 10 minutes after waking. No sleep inertia. Good if you only have a few minutes.
Power nap
Wake at,
The classic. Long enough to enter stage N2 (stable sleep), short enough to avoid deep sleep. Wake refreshed with no grogginess. The NASA-recommended length (their famous "cockpit nap" study found 26 minutes optimal).
Stretch nap
Wake at,
A 30-minute nap risks pulling you into early deep sleep. Some people benefit; others feel groggy on waking. Try once before relying on it regularly.
Full cycle nap
Wake at,
A complete sleep cycle: through deep sleep, into REM, and out. Wake during light sleep, refreshed. Great for memory consolidation and creative work. Don't nap this long after 3 PM, it eats into your nighttime sleep.
Nap length cheat sheet
Each duration corresponds to a different sleep stage, and a different post-nap experience.
| Length | Stages reached | You wake feeling | Best for |
|---|---|---|---|
| 5–10 min | N1 (light sleep) | Slightly refreshed | Quick alertness boost |
| 20 min | N1 + early N2 | Sharply alert, no grogginess | The classic power nap |
| 30 min | Late N2, sometimes early N3 | Variable, risk of grogginess | Moderate sleep debt (caution) |
| 40–80 min | Deep N3 sleep | Very groggy, avoid | Don't nap this length |
| 90 min | Full cycle (N1–REM) | Refreshed, sharper memory | Recovery + creativity |
| 120+ min | Multiple cycles | Risk of nighttime sleep disruption | Severe sleep debt only |
The science of why 20 and 90 work
A sleep cycle progresses through stages in roughly this order: light sleep (N1, a few minutes), stable light sleep (N2, ~10–25 min), deep slow-wave sleep (N3, ~20–40 min), then REM (~10–60 min). The cycle ends back near light sleep, where waking is easy.
Twenty minutes catches you in the early part, pure light sleep, easy to wake. Ninety minutes catches you at the natural end of the cycle, also easy to wake. Anywhere in between, you're in deep N3, and waking from there is genuinely awful.
How a nap affects your night's sleep
Naps draw down your sleep pressure, the build-up of adenosine that makes you sleepy at night. A short early-afternoon nap barely dents it, so it won't hurt your nighttime sleep. But a long nap, or any nap after about 3 PM, can leave you without enough sleep pressure at bedtime, making it harder to fall asleep. This is why people with insomnia are usually advised to avoid napping entirely: protecting nighttime sleep pressure is part of the cure. If you sleep well at night and just want an afternoon boost, a 20-minute nap before 3 PM is essentially free.
Adults vs. children: different nap rules
Everything on this page applies to adults and teens, whose sleep architecture runs on the ~90-minute cycle. Infants and toddlers are completely different, they have shorter cycles, need multiple long naps a day, and follow age-based wake windows rather than cycle math. If you're planning naps for a baby or young child, use our baby sleep calculator instead, which is built around pediatric wake windows from newborn to 18 months.
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Frequently Asked Questions
How long should a nap be?
The two sweet spots are 20 minutes (alertness boost without grogginess) and 90 minutes (a full sleep cycle, ending in REM). Anything between 30 and 80 minutes risks waking you from slow-wave deep sleep, leaving you groggier than before.
Is a 1-hour nap good?
A 60-minute nap is in the danger zone. You're likely to be in deep sleep when the alarm rings, which means severe sleep inertia for 15–30 minutes after waking. If you need a longer nap, stretch it to 90 minutes so you complete the full cycle.
When is the worst time to nap?
Right before bed and right after waking. Napping within 2–3 hours of bedtime can disrupt your nighttime sleep, especially with deep-sleep-heavy naps. Napping immediately after waking doesn't make sense biologically, you haven't built any sleep pressure yet.
Are naps a sign of a sleep problem?
Regular short naps are not, many cultures (Spain, China, Greece) build them into daily life and have similar nighttime sleep duration. However, unintentional daytime sleep, falling asleep during conversation or work, or napping repeatedly for over 90 minutes can indicate undiagnosed sleep apnea, narcolepsy, or chronic sleep deprivation. Talk to a doctor.
Do naps help with stress?
Yes, short naps reduce cortisol and improve emotional regulation. A 30-minute nap was shown in one study to reverse the cortisol elevation from a prior night of insufficient sleep. Even 10 minutes of true sleep produces measurable parasympathetic activation.
Can babies and toddlers nap with the same logic?
No, infants and toddlers have entirely different sleep architecture and need much longer, more frequent naps. Use our Baby Sleep Calculator for age-specific wake windows and nap schedules from 0–18 months.