Sleeptly

Nap calculator

Nap the right length, not the wrong one.

A 20-minute nap leaves you sharper. A 45-minute nap leaves you groggy for an hour. Pick a length and the calculator tells you when to set the alarm.

We add 7 minutes to fall asleep (naps usually drift faster than night sleep).

Power nap
3:15 PM

20-min nap · Quick alertness boost without entering deep sleep.

Short nap
3:25 PM

30-min nap · Light refresh; right on the edge of slow-wave sleep.

Long nap
3:55 PM

60-min nap · Cognitive boost via slow-wave sleep.

Full cycle nap
4:25 PM

90-min nap · Complete one full sleep cycle including REM.

The four nap lengths

Power nap · 20 min

Quick alertness boost without entering deep sleep.

Pros

  • No grogginess on wake
  • Improves alertness and mood
  • Easy to fit into a workday

Cons

  • Limited memory consolidation

Short nap · 30 min

Light refresh; right on the edge of slow-wave sleep.

Pros

  • Better memory than a 10-min nap

Cons

  • Mild sleep inertia risk if you tip into deep sleep

Long nap · 60 min

Cognitive boost via slow-wave sleep.

Pros

  • Improves declarative memory
  • Restorative

Cons

  • Risk of grogginess (sleep inertia) on wake

Full cycle nap · 90 min

Complete one full sleep cycle including REM.

Pros

  • Wake at end of cycle, minimal inertia
  • Procedural & emotional memory benefits

Cons

  • Hard to fit; may delay nighttime sleep

Frequently asked

How long is the ideal nap?
20 minutes works for most people most of the time. It boosts alertness without entering deep sleep, so you wake up cleanly.
What about a 30-minute nap?
Just on the edge of slow-wave sleep. Slightly more benefit, slightly higher chance of grogginess on wake.
When is a 90-minute nap worth it?
If you’re sleep-deprived and have the time. Completing one full cycle (including REM) gives broader memory and emotional benefits, and you wake at the lighter end of the cycle.
Will napping ruin my night sleep?
If kept under 30 minutes and finished before 3 PM, naps don’t typically reduce sleep pressure enough to hurt nighttime sleep. Long, late naps can.

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