About Sleep Cycle & Bedtime Wake-Up Calculator
Wake up refreshed and eliminate morning grogginess. Calculates optimal sleep and wake times based on natural human 90-minute REM sleep cycles and a standard 14-minute sleep latency period.
Key Capabilities & Features
- Dual modes: "I need to wake up at..." and "If I go to bed now..."
- Calculates exact 90-minute REM sleep cycle intervals
- Accounts for 14-minute average sleep onset latency
- Color-coded recommendations (5–6 cycles for optimal rest)
How to Use Sleep Cycle & Bedtime Wake-Up Calculator
Select Mode
Choose target wake-up time or calculate from right now.
Pick Cycle
Review the recommended bedtimes or wake times.
Set Alarm
Set your alarm for the end of a sleep cycle to wake up refreshed.
Privacy & In-Browser Execution Guarantee
Sleep times and schedules run in-memory on your device.
Frequently Asked Questions
How do 90-minute sleep cycles affect morning energy and alertness?
Human sleep progresses through alternating cycles of light sleep, deep slow-wave sleep, and REM dreaming sleep lasting approximately 90 minutes each. Waking up at the conclusion of a completed 90-minute cycle prevents sleep inertia and grogginess.
What time should I go to bed if I need to wake up at a specific hour?
Enter your desired wake-up alarm time. The calculator calculates optimal bedtimes counting backward in 90-minute cycles (typically 4, 5, or 6 cycles, equivalent to 6, 7.5, or 9 hours of sleep), adding an average 15 minutes to fall asleep.
What if I am going to sleep right now—when should I set my alarm?
Use the 'Sleep Now' mode. The calculator checks the current time, adds 14 minutes for sleep onset latency, and displays the exact alarm times when you will naturally surface from light sleep.