Sleep Calculator — Best Bedtime & Wake-Up Times
Find the best time to fall asleep or wake up based on natural 90-minute sleep cycles, so you wake between cycles instead of in the middle of one.
What it does
Sleep Calculator works backwards from your wake-up time (or forwards from now) in 90-minute cycles, accounting for the 15 minutes the average person needs to fall asleep, and suggests bedtimes that align with the end of a complete sleep cycle.
When to use it
Use it the night before an early flight, exam, big meeting — or whenever you want to wake up refreshed instead of groggy.
Benefits
- Based on the 90-minute REM cycle
- Two modes: wake-up time or sleep-now
- Highlights 5–6 cycle sweet spots
- Accounts for falling-asleep time
Example
Want to wake at 6:30 AM? The calculator suggests bedtimes of 9:15 PM or 10:45 PM for a full 6 or 5 sleep cycles.
Frequently asked questions
- Why 90 minutes?
- A typical sleep cycle (light → deep → REM) lasts about 90 minutes. Waking between cycles feels easier than waking mid-cycle.
- Why subtract 15 minutes?
- Research suggests the average healthy adult takes 10–20 minutes to fall asleep. We use 15 as a middle ground.
- Is this medical advice?
- No — it's a general guide based on common sleep science. Consult a doctor for sleep disorders.
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