Sleep Calculator
Find the best times to wake up or go to bed based on 90-minute sleep cycles — waking between cycles means you feel more refreshed.
What Does This Tool Do?
Find the optimal bedtime or wake-up time based on 90-minute sleep cycles. Waking at the end of a complete cycle means you feel more rested — this calculator shows all options with the recommended 6-cycle timing highlighted.
Key Features
Sleep Cycles
Based on 90-minute REM/NREM cycle science.
Both Directions
Find bedtime from wake-up, or vice versa.
Recommended
Highlights the ideal 6-cycle (7.5 hr) option.
Full Table
All cycle options shown simultaneously.
How to Use
- Select Find Bedtime or Find Wake-Up Time.
- Enter your wake-up time or intended sleep time.
- Click the button to see all optimal sleep times.
Frequently Asked Questions
Why 90 minutes?▾
The average human sleep cycle is approximately 90 minutes, cycling through light sleep, deep sleep and REM. Waking mid-cycle causes grogginess (sleep inertia).
How many hours of sleep do I need?▾
Most adults need 7–9 hours (5–6 cycles). The calculator highlights 6 cycles (7.5 hrs) as the recommended target for most people.
Why add 14 minutes?▾
The average person takes about 14 minutes to fall asleep after lying down. This is subtracted from the target to get the recommended bedtime.
Complete Guide to Sleep Calculator
When To Use This Tool
Use Sleep Calculator whenever you need fast, accurate output without installing software. This tool is designed for speed, clarity, and repeatable results for day-to-day work.
Best Practices for Accurate Results
- Double-check the format of your input before running the tool.
- Test with a small sample first, then process larger data.
- Use Related Tools to verify, convert, or transform the output.
Why Users Prefer AdeDX
AdeDX tools are browser-based, free to use, and built to work across desktop and mobile devices. Most processing happens directly in your browser for fast performance and improved privacy.