Free to use, no account
Sleep calculator
Choose a reference time, how long you want to sleep, and how long you usually take to fall asleep. Get a suggested bedtime or wake-up time without claiming exact sleep cycles.
Suggested time
This is simple time arithmetic based on your choices, not a prediction of sleep cycles or a medical recommendation. Sleep needs vary by age and person.
How does this sleep calculator work?
Choose a wake-up time to calculate when to get into bed, or choose a bedtime to estimate a wake-up time. The result adds or subtracts your selected sleep duration and time to fall asleep, including when the clock crosses midnight.
Frequently asked questions
How does this sleep calculator work?
Choose a wake-up time to calculate when to get into bed, or choose a bedtime to estimate a wake-up time. The result adds or subtracts your selected sleep duration and time to fall asleep, including when the clock crosses midnight.
Is this sleep calculator free and private?
Yes. The calculation runs in this browser. No account or upload is needed, and your entries are not saved.
Does this calculate exact 90-minute sleep cycles?
No. Sleep cycles vary and are not reliably predicted by a fixed 90-minute rule. This tool only adds or subtracts the sleep duration and time to fall asleep that you enter.
What does time to fall asleep mean?
It is the number of minutes you choose to allow between getting into bed and falling asleep. The result includes it so the planned sleep duration starts after that interval.
How much sleep should I get?
Sleep needs vary with age and individual circumstances. This calculator does not prescribe a duration; ask a qualified healthcare professional if you have sleep or health concerns.