Health tool
Sleep cycle calculator
Work out good times to wake up or go to bed, based on 90-minute sleep cycles.
Calculator
What is a sleep cycle
Sleep moves through light sleep, deep sleep, and REM in rounds called cycles. One full cycle averages about 90 minutes — commonly somewhere between 80 and 120 minutes depending on the person and the night. Waking near the end of a cycle usually feels easier than being pulled out of deep sleep.
How to use it
- Pick a mode: plan a bedtime, or set a required wake-up time.
- Enter the time, and adjust the minutes it usually takes you to fall asleep.
- Calculate to see several candidate times, each labeled with its cycle count and total sleep.
Aim for 5–6 cycles (about 7.5–9 hours), which lines up with the sleep duration most adults are advised to get. 4 cycles is about 6 hours — a bit tight. 3 cycles is about 4.5 hours and is not a pattern to rely on.
Frequently asked questions
Is a sleep cycle always 90 minutes?
No. 90 minutes is a population average. Individual cycles commonly run 80–120 minutes and vary across the night. This tool estimates from the average, so treat results as a reference.
What is the best time to wake up?
There is no single best wake-up time. What matters more is getting enough sleep, waking near the end of a cycle, and keeping a regular schedule. Most health bodies advise adults to sleep 7–9 hours.
How long does it take to fall asleep?
Most adults fall asleep about 10–20 minutes after lying down. The tool assumes 15 minutes; adjust it to your own experience.
What if the result does not match how I feel?
Cycle length, sleep quality, caffeine, and noise all affect how you wake. If you regularly sleep badly or feel very sleepy during the day, talk to a doctor instead of only shifting times.
Is it bad to sleep only 3–4 cycles?
An occasional short night is fine, but chronic short sleep is linked to attention, mood, and cardiovascular risks. Aim to get enough most nights.
Can weekend catch-up sleep fix sleep debt?
It can ease sleepiness, but swinging between schedules disrupts your body clock. A steady bedtime and wake time matters more than catching up.