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Nap Duration Calculator

Work out nap duration instantly with clear inputs, formula shown and shareable results.

About Nap Duration Calculator

Naps work best either short or complete. Under 20-25 minutes you stay in light sleep and wake refreshed; between 30 and 60 minutes you wake from slow-wave sleep feeling worse than before. A full 90 minute cycle avoids that entirely.

Formula

Nap timing

alarm = target nap length + time to fall asleep; target is 20 min or a full 90 min cycle

Worked example

With the default values below, Nap Duration Calculator returns Recommended nap length of 20. Change any input above and every figure here is recalculated in your browser.

Inputs used

Nap purposeone of Power nap (alertness), Recovery nap (light sleep), Full cycle nap, Long recovery (two cycles)
Power nap (alertness)
Time available
45 min
Time to fall asleep
8 min

Results

Recommended nap length
20 min
Set the alarm for
28 min
Expected sleep inertia
Minimal - stays in light sleep
Fits the time available
Fits within the time available

Step by step

  1. 1Values used
  2. 2Nap timing
  3. 3Recommended nap length= 20 min
  4. 4Set the alarm for= 28 min
  5. 5Expected sleep inertia= Minimal - stays in light sleep
  6. 6Fits the time available= Fits within the time available

Assumptions and limits

  • The result is derived only from the 3 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to whole numbers, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

Why is a 45 minute nap the worst option?

It lands you in deep slow-wave sleep at the moment the alarm goes off, producing 15-30 minutes of heavy sleep inertia.

When should I stop napping in the day?

Generally by early afternoon. Later naps eat into the sleep pressure that helps you fall asleep at night.

Related Calculators

Nap Duration Calculator – Calculate Recommended nap length