Free tools
Calculators that run in your browser. No sign-up, nothing stored on a server, and the method and sources are on each page.
- Sleep calculator
Bedtimes and wake times that land between 90-minute cycles.
- Caffeine cutoff calculator
When your last coffee should be, based on half-life and bedtime.
- Chronotype quiz
Find your chronotype from when you sleep on free days.
- Jet lag planner
When to seek and avoid light after crossing time zones.
- Daylight planner
Sunrise, sunset and your morning-light window for any date.
- Nap calculator
Pick a nap length that does not leave you groggy.
- Light levels chart
How bright common places are, in lux.