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Calculators/Everyday
Sleep Calculator
Find the best bedtime or wake-up time based on 90-minute sleep cycles. Wake up feeling refreshed by timing your sleep to complete full cycles.
Bedtime Options
12:45 AM
4 cycles · 6h sleep11:15 PMRecommended
5 cycles · 7.5h sleep9:45 PM
6 cycles · 9h sleep8:15 PM
7 cycles · 10.5h sleepRecommended Bedtime
11:15 PM
Sleep Cycles
5 cycles
Total Sleep
7.5 hours
How to Use This Calculator
1
Choose your mode
Use 'Wake at' mode if you have a fixed wake time and want to know when to go to bed. Use 'Sleep now' mode to find the best wake-up times if you're about to sleep.
2
Understanding sleep cycles
The average sleep cycle lasts 90 minutes. Each cycle moves through light sleep, deep sleep, and REM sleep. Waking mid-cycle causes grogginess; waking at the end of a cycle feels natural.
3
Choose the right number of cycles
Most adults need 5–6 cycles (7.5–9 hours). 4 cycles (6 hours) works for short nights. 7 cycles (10.5 hours) is for recovery after sleep debt. The 5-cycle option is highlighted as the recommended target.
Real-World Examples
Morning Meeting at 7 AM
Mode
Wake At
Wake Time
7:00 AM
ResultBedtime: 11:15 PM
5 cycles × 90 min + 15 min to fall asleep = 7 hours 45 min before alarm.
Going to Sleep at Midnight
Mode
Sleep Now
Current Time
12:00 AM
ResultWake up: 7:45 AM
5 cycles from midnight + 15 min to fall asleep = wake at 7:45 AM feeling rested.
Frequently Asked Questions
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