Calculators
Sleep Calculator
Bedtime / wake-up times around 90-minute cycles
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How long does it take you to fall asleep?
min
How many hours do you like to sleep?
h
The two cycle options closest to this target are flagged Ideal.
6 options
Targeting — the two cycle options closest to that are flagged below as Ideal. The other four are useful for power naps or emergency short sleeps.
— shorter sleep · power naps
Your sleep
light → deep → repeat
bed
wake
Light · REM
Deep
Now
Sleep happens in roughly 90-minute cycles. Waking at the end of a cycle (rather than mid-cycle) helps you feel rested. Tap Add to calendar on an Ideal time to download an
.ics reminder with a 0-minute alarm.
About this tool
Plan your bedtime — or your alarm — around full 90-minute sleep cycles so you wake at the end of a cycle rather than mid-dream. Pick a wake-up time and the calculator suggests four bedtimes; pick a bedtime and it suggests four wake-up times. The 7.5 h and 9 h options (5 and 6 cycles) are flagged as Ideal for most adults.
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Formula
Bedtime = wake time − (cycles × 90 min) − fall-asleep time
Wake time = bedtime + fall-asleep time + (cycles × 90 min)
Most adults: 5 or 6 cycles = 7.5–9 hours
How to use
- 1 Pick the mode: I want to wake up at… or I’m going to bed at…
- 2 Enter the time. Tap Now to set it to the current time.
- 3 If it usually takes you longer or shorter to fall asleep, adjust the fall-asleep buffer (default 15 min).
- 4 Read the four suggested times. The Ideal-flagged ones (5–6 cycles) are the recommended targets for most adults.
Examples
| Want to wake at 6:30 AM, 15-min fall-asleep buffer | Try bed at 9:15 PM (6 cycles · 9 h), 10:45 PM (5 cycles · 7.5 h), 12:15 AM (4 cycles · 6 h) |
| Going to bed at 11:00 PM, 15-min fall-asleep buffer | Wake at 6:30 AM (5 cycles · 7.5 h) or 8:00 AM (6 cycles · 9 h) |
| Power nap — bed at 1:00 PM, 5-min fall-asleep | Wake at 2:35 PM (1 cycle · 1.5 h) feels best for cognitive recovery |
Frequently asked questions
Adult sleep cycles average about 90 minutes — passing through light, deep and REM stages. Waking near the end of a cycle (when sleep is lightest) feels much less groggy than being jolted out of deep sleep mid-cycle.
Most adults function best on 7–9 hours (5 or 6 cycles). Teens and young adults often need 8–10. Newborns need 14–17. The 4.5 h and 6 h options are emergency targets, not a healthy routine.
Healthy adults take roughly 10–20 minutes to fall asleep. The buffer pushes the actual sleep math back so the suggested bedtime is the time you should be in bed, not the time you should already be asleep.
No — they range from about 70 to 120 minutes and lengthen toward morning. 90 minutes is a useful average; treat the suggestions as a guide, not a guarantee.
No, it only computes the times. Set the alarm yourself in your phone or smart-watch.
Related tools
Heads up: 90-minute cycles are an average — your actual sleep architecture varies by age, health, caffeine, and genetics. Persistent insomnia, daytime sleepiness, snoring or sleep apnea symptoms need a sleep specialist, not a bedtime calculator.
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Sleep Calculator
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