Sleep Cycle Calculator - Free Online Tool | PivaBox

Calculate optimal sleep and wake times based on 90-minute sleep cycles to wake up refreshed

How to Use Sleep Cycle Calculator

1. Choose your mode: "What time should I wake up?" (enter bedtime) or "What time should I go to bed?" (enter desired wake time)
2. Enter your bedtime or wake time, or click Current Time to fill it automatically
3. Review the 6 recommended times — each represents waking up at the end of a sleep cycle. Green-highlighted options (5-6 cycles / 7.5-9 hours) are the most recommended for adults.

Frequently Asked Questions

Is Sleep Cycle Calculator free?

Yes, PivaBox Sleep Cycle Calculator is completely free to use. All calculations happen locally in your browser.

Why 90-minute sleep cycles?

The average human sleep cycle lasts approximately 90 minutes and includes all sleep stages (light sleep, deep sleep, and REM). Waking up at the end of a cycle — rather than in the middle — helps you feel more refreshed and less groggy.

Does the calculator account for falling asleep time?

Yes, the calculator automatically adds 15 minutes for the average time it takes to fall asleep. For example, if you want to wake up at 7:00 AM, the calculator recommends bedtimes that give you complete sleep cycles plus 15 minutes to drift off.