Calculate optimal times to wake up or go to bed to feel refreshed.
How to Use Sleep Calculator
Choose whether you're setting a wake-up time or a bedtime.
Enter that time - the tool calculates several alternative times based on complete 90-minute sleep cycles.
Pick whichever suggested time aligns best with when you need to be up or asleep.
Key Features & Practical Use Cases
Calculating the perfect bedtimes to complete full REM sleep cycles without waking up groggy.
Determining exactly what time to set an alarm to wake up feeling refreshed.
Tracking total hours slept to ensure you meet optimal health and rest guidelines.
Frequently Asked Questions
Why does it suggest times in roughly 90-minute increments?
A full sleep cycle (light sleep through REM) is commonly estimated at about 90 minutes - waking up at the end of a complete cycle, rather than mid-cycle, is associated with feeling less groggy.
Does it account for the time it takes to actually fall asleep?
The suggested bedtimes typically build in a short buffer (commonly ~15 minutes) for falling asleep before the first cycle begins - check the specific note shown alongside your results.
Can I use this to plan a nap instead of a full night's sleep?
This tool is designed around full multi-cycle overnight sleep; for short naps, a single shorter fixed duration (like 20 minutes) is generally recommended instead of cycle-based timing.
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