title

Use this free sleep calculator to find the best bedtime or wake time based on 90-minute sleep cycles.
currentTime
aboutTitle

Sleep cycles typically last 90 minutes and include different stages of sleep.

Sleep Cycle Stages:

  • Light Sleep: Transition phase, easy to wake up
  • Deep Sleep: Physical recovery and growth
  • REM Sleep: Mental consolidation and dreaming

Optimal Sleep:

  • 5-6 cycles: 7.5-9 hours - Most adults' optimal range
  • 4 cycles: 6 hours - Minimum for most adults
  • 3 cycles: 4.5 hours - Not recommended long-term

Tips for Better Sleep:

  • Maintain consistent sleep schedule
  • Avoid screens 1 hour before bed
  • Keep bedroom cool and dark
  • Avoid caffeine late in the day
  • Exercise regularly but not before bed

This calculator assumes 15 minutes to fall asleep. Individual sleep needs may vary based on age, genetics, and lifestyle.

i

How our sleep calculator works

1

Choose a wake time or bedtime

Type your desired wake time (e.g. 7 AM) or bedtime (e.g. 11 PM). The calculator will suggest the optimal other end of your sleep window.

2

We apply 90-minute sleep cycles

A full sleep cycle is about 90 minutes, moving through light, deep, and REM sleep. Waking between cycles feels more refreshed than waking mid-cycle.

3

Pick your cycle count

Choose 4, 5, or 6 cycles (6h, 7.5h, 9h). We suggest wake times that align with cycle ends and add 15 minutes for falling asleep.

Key things to know about our sleep calculator:

  • Most adults need: 7-9 hours of sleep per night. The 7.5h and 9h options are usually best for full rest. The 6h option is the minimum for one night.
  • Sleep cycles vary: First cycles have more deep sleep, later cycles have more REM. Personal variation is normal; the calculator is a starting point, not a strict rule.
  • Pair with consistency: Going to bed and waking at the same time every day, even weekends, leads to better long-term sleep than varying bedtimes.

For related calculations, try our time calculator.