Is a 90-minute nap good? What happens when you wake up
Updated October 3, 2026 · Sources: NASA 1995 · Brooks & Lack 2006 · Tassi & Muzet 2000 · NINDS
Short answer
90 min
reaches complete cycle including REM · grogginess on waking: low (waking near the end of a cycle). Set the alarm for 105 minutes after you lie down to allow for falling asleep.
General information from population studies (NIH, CDC, NSF, AASM). It is not medical advice and does not replace a clinician who knows you.
Lie down for 90 minutes and you will usually get as far as complete cycle including REM. A 90-minute nap covers roughly one complete sleep cycle, so you tend to wake from light sleep or REM rather than deep sleep. Grogginess afterwards: low (waking near the end of a cycle).
Sleep inertia ratings from Brooks & Lack 2006, Tassi & Muzet 2000, Rosekind 1995 · as of October 3, 2026
Why 90 minutes behaves this way
A full cycle means you pass through light, deep and REM sleep and wake near the end, when sleep is light again. It also costs the most sleep pressure: a 90-minute nap after mid-afternoon can push tonight's bedtime later, so keep it early in the day.
Every nap length
| Nap | Reaches | Grogginess | Set aside |
|---|---|---|---|
| 10 min | light sleep (N1-N2) | minimal | 25 min |
| 20 min | light sleep (N2) | low | 35 min |
| 26 min | light sleep, occasionally early deep sleep | low to moderate | 41 min |
| 30 min | often enters deep sleep (N3) | moderate | 45 min |
| 45 min | deep sleep (N3) likely | moderate to high | 60 min |
| 60 min | deep sleep (N3) | high | 75 min |
| 90 min | complete cycle including REM | low (waking near the end of a cycle) | 105 min |
15 minutes added for sleep onset · sources above · as of October 3, 2026
Sources
- A brief afternoon nap following nocturnal sleep restriction: which nap duration is most recuperative? — Sleep 29(6):831-840, 2006 (Brooks A., Lack L.)
- Alertness Management: Strategic Naps in Operational Settings — NASA Technical Memorandum 108839 (Rosekind M.R. et al.), 1995; also J Sleep Res 4(S2):62-66
- Sleep inertia — Sleep Medicine Reviews 4(4):341-353, 2000 (Tassi P., Muzet A.)
- Brain Basics: Understanding Sleep — NINDS (NIH)
General information from population studies (NIH, CDC, NSF, AASM). It is not medical advice and does not replace a clinician who knows you.