Bedtime Calculator
Sleep happens in ~90-minute cycles. Working backward from your alarm helps you wake between cycles.
When do you need to wake up?
About this bedtime calculator
Sleep cycles last about 90 minutes. Waking between cycles — rather than in deep sleep — often means less grogginess.
Work backward from your wake-up time to find bedtimes that align with 4, 5, or 6 full cycles, plus ~15 minutes to fall asleep.
Consistent sleep and wake times support circadian rhythm, mood, and blood pressure regulation.
Frequently asked questions
What time should I go to bed? +
Depends on when you need to wake. This calculator suggests bedtimes for 4–6 sleep cycles based on your alarm time.
How many hours of sleep do adults need? +
Most adults need 7–9 hours. Quality and consistency matter as much as total hours.
Why do I wake up tired after 8 hours? +
Waking mid-cycle, poor sleep quality, sleep apnea, or inconsistent schedules can cause this. Talk to your doctor if fatigue persists.
Related health guides
Try these next