Is a 20-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
20 min
reaches light sleep (N2) · grogginess on waking: low. Set the alarm for 35 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.
A 20-minute nap normally reaches light sleep (N2). Benefits appeared after about 35 minutes of grogginess cleared, then lasted up to 2 hours; the classic 'power nap' length in workplace guidance. Expect low grogginess on waking.
Sleep inertia ratings from Brooks & Lack 2006, Tassi & Muzet 2000, Rosekind 1995 · as of October 3, 2026
Why 20 minutes behaves this way
Short naps stay in light sleep, which is the whole trick: there is nothing deep to wake up from, so the benefit arrives almost immediately. In the Brooks and Lack comparison, 10 minutes outperformed 20 and 30 on immediate alertness because it avoided sleep inertia entirely.
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.