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.
Plan Your Sleep
To wake at 07:00, fall asleep at one of these times (15 min to fall asleep included):
21:45
9 hours of sleep · 6 cycles
fall asleep by
23:15
7 hours 30 min of sleep · 5 cycles
fall asleep by
00:45
6 hours of sleep · 4 cycles
fall asleep by
To wake at 07:00, be asleep by 21:45 (6 cycles), 23:15 (5 cycles) or 00:45 (4 cycles).
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
Related tools
FAQ
Common questions about Sleep Calculator
How we calculate this
We use the standard published formula for this calculation, and we show the working so you can check it.
Spotted a mistake? Tell us and we'll check it within a few days. See how we check our calculators.