OmniCalcsSleep Cycle Calculator
Wake up at the end of a sleep cycle — not in the middle — and feel dramatically more rested.
How to Use This Calculator
Choose the wake-time mode to get bedtimes that end your cycles at your target wake time. Choose the bedtime mode to get ideal wake times. Either way, plan for 5 to 6 full cycles.
- Count back 15 minutes of "falling asleep" time in the calculation.
- Consistency — same bed and wake times daily — beats perfect timing.
Frequently Asked Questions
How long is a sleep cycle?
Roughly 90 minutes for adults, varying from 70 to 120 minutes. Most people complete 4-6 cycles per night.
Why do I still feel tired after 8 hours?
You may be waking in the middle of a cycle. Aligning your wake time to a cycle boundary often fixes that groggy feeling.
Is 7.5 hours the magic number?
Most adults need 7-9 hours. Five 90-minute cycles (7.5 h) is a common sweet spot, but individual needs vary.
Does this work for everyone?
Cycle length varies by person. If you often wake mid-cycle, adjust the estimate by tracking when you naturally wake.
Practical Example
To wake at 7:00 AM, choose the 5-cycle option (7.5 hours of sleep). Counting back the 15 minutes it takes to fall asleep plus 5 × 90 = 450 minutes of sleep gives a bedtime of 11:15 PM — that is 7:00 AM minus 7 hours 45 minutes. The 6-cycle option (9 hours) puts bedtime at 9:45 PM, and the 4-cycle option (6 hours) at 12:45 AM.
- Pick the "I'm going to bed now" mode with a 23:00 bedtime to see the matching wake times of 5:15, 6:45, and 8:15 AM.
What Your Results Mean
- Bedtime / wake time — the clock time that ends a whole number of 90-minute cycles, plus 15 minutes to fall asleep, at your target.
- Number of cycles — 5 to 6 cycles (7.5 to 9 hours) is the recommended target for most adults.
- Feeling refreshed — waking at a cycle boundary avoids the grogginess of waking mid-cycle, though individual cycle lengths vary.