Sleep Cycle Calculator
Formula
Wake Time = Bedtime + (Cycles × 90min) + 15min
Sleep cycles last roughly 90 minutes. Waking between cycles helps you feel refreshed. 15 minutes is added for falling asleep. The recommended option (5 cycles = 7.5 hours) is shown as the primary answer.
Frequently Asked Questions
How many sleep cycles do I need?
Most adults need 5-6 cycles (7.5-9 hours). 4 cycles (6 hours) is the minimum for function.
Why 90-minute cycles?
Each cycle goes through light sleep, deep sleep, and REM. Waking mid-cycle (especially deep sleep) causes grogginess.
What does the 15 minutes account for?
The average person takes about 15 minutes to fall asleep. The wake times are calculated from when you actually fall asleep, not when you get into bed.