Sleep Calculator

How does the sleep calculator work?

A full sleep cycle lasts about 90 minutes and goes through light sleep, deep sleep and REM sleep. This free calculator adds about 15 minutes for falling asleep and then works backwards from your wake-up time — or forwards from your bedtime — to recommend schedules that end at the natural end of the 5th or 6th cycle.

How to use

• Choose the wake-up mode to get recommended bedtimes, or the bedtime mode for wake-up suggestions.
• Pick a time with the time input.
• Read the suggestions for 5 and 6 sleep cycles.
• Copy the full list with one click and follow the schedule that fits your life.

FAQ

• Why are 5 or 6 cycles recommended? Waking up inside deep sleep makes you groggy, while waking between cycles leaves you more alert. With 5 cycles you sleep about 7.5 hours and with 6 about 9 hours, plus roughly 15 minutes to fall asleep.
• Do I have to start in bed exactly at the suggested time? No. The suggested bedtime is when you should aim to fall asleep about 15 minutes later. Falling asleep a few minutes off is fine — consistency matters more than a perfect minute.
• Can I use it if I sleep less than 5 cycles? It works with any wake-up or bedtime you enter. Staying within complete cycles is ideal, but a 4-cycle night is still calculated correctly if that is what your schedule allows.