Sleep Calculator
Find the best time to sleep or wake up based on sleep cycles. Free, fast and private.
Your result will appear here.
Based on 90-minute sleep cycles. Most adults need 4–6 cycles (6–9 hours).
How to use Sleep Calculator
- Choose whether you want to set a wake-up time or a bedtime.
- Enter the time.
- Click Calculate Sleep Times to see the best bedtimes or wake-up times based on 90-minute sleep cycles.
Note: this tool runs in your browser. Nothing is uploaded.
Frequently Asked Questions
What is a sleep cycle?
A sleep cycle lasts about 90 minutes. Waking up at the end of a cycle usually feels fresher than waking mid-cycle.
How many cycles do I need?
Most adults need 4–6 cycles, which is 6–9 hours of sleep, plus about 15 minutes to fall asleep.
Should I set a wake-up time or a bedtime?
Either works. Pick a wake-up time to find the best bedtimes, or a bedtime to find the best wake-up times.
Is this medical advice?
No. This is a general guide based on average 90-minute cycles. If you have sleep problems, speak to a doctor.