The Optimal-Sleep-Calculator lets you know what time you should wake up if you go to sleep now. It runs on the idea that REM cycles typically last anywhere from 80 to 100 minutes. An initial time to fall asleep variable of 14 minutes is also included.
This calculator was developed as I often find myself on my computer late at night and do not like waking up sleepy and tired. This calculator allows me to check what time I should set my alarm clock for.
Just open the index.html file in any browser.