Everyday & lifestyle · Fun Misc
Sleep Calculator
Find the best times to wake up or go to sleep based on 90-minute sleep cycles. Waking at the end of a cycle feels more refreshing. Free sleep cycle calculator.
How it works
Calculates optimal sleep or wake times based on 90-minute sleep cycles. Each full cycle includes light sleep, deep sleep, and REM sleep. Waking between cycles (rather than during them) typically feels more refreshing.
Step by step
- 1Choose whether you want wake-up times (given your bedtime) or bedtimes (given your wake-up time).
- 2Enter the relevant time and how long you typically take to fall asleep.
- 3The tool calculates times aligned with 4, 5, and 6 complete 90-minute sleep cycles.
- 4Aim for 5–6 cycles (7.5–9 hours) for most adults.
Examples
Bedtime 23:00, when to wake
23:00 + 14 min + 6×90 min = 06:14 for 6 full cycles.
Inputs
- mode:
- wake
- bedtime:
- 23:00
- fall_asleep_minutes:
- 14
Result
- options:
- 06:14 (6 cycles) · 04:44 (5 cycles) · 03:14 (4 cycles)
Frequently asked questions
Why 90-minute cycles?▾
A typical sleep cycle lasts ~90 minutes and includes light sleep, deep sleep (slow-wave), and REM (rapid eye movement) sleep. Waking at the end of a cycle, when you're in light sleep, tends to feel more natural and less groggy than being woken during deep sleep.
How many sleep cycles do I need?▾
Most adults need 5–6 cycles per night (7.5–9 hours). Teenagers may need 6–8 cycles. Athletes and people recovering from illness often benefit from extra sleep.