Health & Fitness
Sleep Calculator
Pick when you need to wake up — or when you are going to bed — and get times that line up with complete sleep cycles.
For information only. Results are estimates and are not medical advice. Please talk to a doctor or qualified professional about your own health.
About the Sleep Calculator
A sleep cycle lasts about 90 minutes, and most adults need 5–6 cycles (7.5–9 hours). Waking at the end of a cycle often feels easier than waking in deep sleep.
We assume it takes about 15 minutes to fall asleep. Everyone differs, so adjust the times to what works for you.
Frequently asked questions
How many hours of sleep do adults need?
Most adults need 7–9 hours a night.
Why do I feel tired after 8 hours?
Sleep quality, stress, caffeine, screens before bed and underlying conditions all matter as much as duration. If tiredness persists, see a doctor.