Sleep Cycle Calculator
Find bedtimes and wake times based on 90-minute cycles.
Bedtimes that complete full 90-minute cycles (with 15-min buffer to fall asleep). Top option is most rested.
Go to bed at
9:45 PM
6 cycles
9.0 hr sleep
Go to bed at
11:15 PM
5 cycles
7.5 hr sleep
Go to bed at
12:45 AM
4 cycles
6.0 hr sleep
Go to bed at
2:15 AM
3 cycles
4.5 hr sleep
About
Waking up mid-cycle leaves you groggy. Waking between cycles feels much better. This calculator works both ways. Tell it when you want to wake up and it shows bedtimes that complete full 90-minute cycles. Tell it you're going to bed now and it suggests wake times.
How to use
- Pick a mode: 'I want to wake up at...' or 'I'm going to bed now'.
- If choosing a wake time, enter it. If going to bed now, the calculator uses the current time.
- A 15-minute buffer is added for falling asleep, then 5 suggested times line up with full cycles.
FAQ
Why 90 minutes?+
A full sleep cycle (light to deep to REM to light) takes roughly 90 minutes for most adults. Waking at the end of a cycle, in light sleep, feels much better than waking mid-cycle in deep or REM sleep.
Why the 15-minute buffer?+
The average person takes 10 to 20 minutes to fall asleep after going to bed. 15 minutes is a reasonable middle estimate.
How many cycles do I need?+
5 to 6 cycles (7.5 to 9 hours) is the sweet spot for most adults. 4 cycles (6 hours) works for some people but most will be tired. 3 cycles is a stopgap, not a sustainable plan.