Sleep Calculator
Find the best bedtime or wake-up time based on 90-minute sleep cycles.
Reviewed by the WorldCalcs team · Methodology · Last reviewed: June 2026
6 cycles — go to bed at
6 × 90 min + 15 min to fall asleep
9:45 pm
Recommended
5 cycles — go to bed at
5 × 90 min + 15 min to fall asleep
11:15 pm
Recommended
4 cycles — go to bed at
4 × 90 min + 15 min to fall asleep
12:45 am
What is a sleep calculator?
A sleep calculator suggests the best times to go to bed or wake up so that you wake at the end of a sleep cycle rather than in the middle of one, which can help you feel more rested.
How it works
Sleep runs in cycles of about 90 minutes. The tool counts back (or forward) in 90-minute blocks and adds about 15 minutes to fall asleep. Aiming for 5–6 full cycles (about 7.5–9 hours) is ideal for most adults. Example: to wake at 7:00 am, good bedtimes are around 9:45 pm (6 cycles) or 11:15 pm (5 cycles).
All calculations happen in your browser. Nothing is sent, stored, or tracked.
Results are estimates and may contain errors — for general information only, not professional advice. Always verify before relying on them. Disclaimer
How to use
Choose whether you want to set a wake-up time or a bedtime, then pick your time. The calculator shows recommended times for 4, 5 and 6 sleep cycles, including about 15 minutes to fall asleep.
Aim for 5–6 full cycles (about 7.5–9 hours) for most adults. Waking at the end of a cycle tends to feel easier.