Wake up feeling refreshed by aligning your sleep with natural 90-minute cycles. Choose a mode below to find optimal bedtimes or wake times.
Recommended Bedtimes
This calculator provides estimates and is for informational purposes only. Consult a healthcare professional for medical advice.
How It Works
Sleep occurs in 90-minute cycles, each consisting of light sleep, deep sleep, and REM stages. Waking up at the end of a complete cycle — rather than in the middle of one — helps you feel refreshed and alert instead of groggy.
This calculator factors in an average of 14 minutes to fall asleep and works backward (or forward) from your target time to find the optimal points that align with complete sleep cycles. Most adults need 4 to 6 full cycles (6 to 9 hours) per night for optimal health and cognitive function.
Frequently Asked Questions
How many hours of sleep do I need?
Most adults need 7–9 hours (5–6 complete cycles) per night. Teenagers need 8–10 hours, and children need even more. Consistently getting fewer than 6 hours is associated with increased health risks.
Why do I feel tired even after 8 hours of sleep?
You may be waking up mid-cycle. Aligning your sleep with 90-minute cycles helps you wake during lighter sleep stages, reducing grogginess. Sleep quality, consistency, and environment also play important roles.
Does it really take 14 minutes to fall asleep?
The average healthy adult takes 10–20 minutes to fall asleep (sleep latency). We use 14 minutes as a reasonable average. If you fall asleep much faster or slower, you can mentally adjust the times by a few minutes.