Sleep Cycle Calculator
Find the best bedtime or wake-up time based on 90-minute sleep cycles.
Waking up groggy often isn't about how long you slept but when in a sleep cycle you woke. Sleep runs in roughly 90-minute cycles through light, deep and REM stages; waking at the end of a cycle — in light sleep — leaves you refreshed, while waking mid-cycle from deep sleep leaves you foggy for the morning.
Tell this calculator when you need to wake up and it works backwards to suggest bedtimes that land you at the end of complete cycles (with ~15 minutes to fall asleep factored in). Or give it a bedtime and it suggests the best times to set your alarm. Aim for the options giving 5–6 cycles (7.5–9 hours) for most adults.
How to use Sleep Cycle Calculator
- 1
Choose a direction
"I want to wake at…" or "I'll sleep at…".
- 2
Enter the time
Your target wake-up or bedtime.
- 3
Pick a suggested time
Each aligns with the end of a sleep cycle.
Features
- Works forward or backward
- Based on 90-minute cycles
- Accounts for ~15 min to fall asleep
Frequently asked questions
Common mistakes to avoid
- Treating 90 minutes as exact — individual cycles vary; use the suggestions as a starting point.
- Optimizing cycle timing while ignoring total sleep — 4 well-timed cycles still isn't enough rest.
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