Sleep Calculator
Calculate the best times to go to sleep or wake up based on 90-minute sleep cycles. Wake up refreshed by timing your alarm to the end of a cycle.
How to Use the Sleep Calculator
Use the "When to Sleep" tab to find the best bedtimes if you have a fixed morning alarm. Use the "When to Wake" tab if you know when you are going to bed and want to know the best wake-up times. The calculator builds in 14 minutes for the average time it takes to fall asleep.
The Extended Calculator below shows a visual sleep cycle diagram and optimal bedtime options for 4, 5, and 6 cycles. The Professional Calculator adds chronotype assessment (Lion/Bear/Wolf/Dolphin), sleep debt tracker, jet lag calculator, and polyphasic sleep reference.
Sleep Schedule Guide
| Sleep Duration | Cycles | For |
|---|---|---|
| 6h 00min | 4 cycles | Minimum — not ideal long-term |
| 7h 30min | 5 cycles | Optimal for most adults |
| 9h 00min | 6 cycles | Recovery after intense training or illness |
How Sleep Cycles Work
One Sleep Cycle: 90 minutes
Optimal Sleep: 5–6 complete cycles (7.5–9 hours)
Minimum: 4 cycles (6 hours) — not recommended long-term
Fall-asleep offset: 14 minutes added to bedtime
Each 90-minute cycle progresses through light sleep, deep (slow-wave) sleep, and REM sleep. Waking mid-cycle — especially during deep sleep — causes sleep inertia, the groggy, disoriented feeling you get when your alarm jolts you awake.
Example
Wake-up time: 06:00
6 cycles (9h) → go to bed at 20:46
5 cycles (7.5h) → go to bed at 22:16
4 cycles (6h) → go to bed at 23:46
Ideal wake: 7:00–8:00 | Ideal bedtime: 23:00–00:00 | Peak hours: 10:00–14:00
Sleep Debt Tracker
Jet Lag Calculator
Going east is harder. Expose yourself to bright morning light at destination. Avoid caffeine in evening.
Polyphasic Sleep Reference
| Schedule | Total Sleep | Pattern |
|---|---|---|
| Monophasic (standard) | 8h | One 8h block at night |
| Biphasic (siesta) | 7h | 6.5h night + 20–30min nap |
| Everyman 3 | 5.5h | 4.5h core + 3×20min naps |
| Uberman | 2h | 6×20min naps throughout day — very difficult |
| Dymaxion | 2h | 4×30min naps — very difficult |
Polyphasic schedules beyond biphasic are not well-supported by research for long-term health. Consult a sleep specialist before attempting.