Sleep Calculator
Tell us when you need to wake up and we'll suggest bedtimes that end a sleep cycle, or enter a bedtime to see wake-up times.
Your details
Result
Fall asleep by one of these times
23:15
5 cycles · 7 hours 30 minutes of sleep
| Fall asleep by | Sleep |
|---|---|
| 21:45 | 9 hours of sleep · 6 cycles |
| 23:15 | 7.5 hours of sleep · 5 cycles |
| 00:45 | 6 hours of sleep · 4 cycles |
- Based on 90-minute sleep cycles and 15 minutes to fall asleep. Most adults do best with 7 to 9 hours.
Good to know: To wake at 07:00, be asleep by 21:45 (6 cycles), 23:15 (5 cycles) or 00:45 (4 cycles).
About this tool
Suggests bedtimes or wake times aligned to complete 90-minute sleep cycles, so you wake at the end of a cycle rather than in deep sleep.
Formula
time = target ± (fall-asleep 15 min + cycles × 90 min), for 4, 5 and 6 cycles.
Reference values
- One sleep cycle ≈ 90 minutes
- Adults need 7–9 hours (5–6 cycles)
- Falling asleep takes ~15 minutes on average
Questions people ask
How long is a sleep cycle?
About 90 minutes, though this varies by person and through the night.
Why does timing matter?
Waking at the end of a cycle can feel easier than being woken in deep sleep.
How much sleep do adults need?
Most adults do best with 7 to 9 hours. If you have ongoing sleep problems, speak to a doctor.
Related tools
How we calculate this
We use the standard published formula or definition for this calculation, and we show the working so you can check it.
Spotted a mistake? Tell us and we'll check it. How we check our calculators