Sleep calculator
From alarm to lights-out, or from bedtime to alarm.
- What time should I go to bed?
- When should I set my alarm?
- How many hours do adults sleep?
Home / Tools
Free sleep and caffeine calculators.
Three small tools for the questions people type at midnight: when to turn in, how much coffee is still around, and how far the week ran short. They work in your browser, keep nothing, and ask for nothing.
Caffeine calculator
Log today’s drinks and estimate what may remain at bedtime.
- What is caffeine’s half-life?
- How much is in my coffee?
- Where is my six-hour mark?
Sleep debt calculator
Seven real nights against the target you set.
- How short did my week run?
- What is sleep debt?
- Is sleep debt real?
how we build them
Arithmetic you can check.
- The math is printed on the page.Every tool shows the formula it runs, so you can redo it on paper.
- Research notes link to the source.Each finding carries a numbered citation that opens on our sources page, limits included.
- Your numbers stay with you.Nothing you type is stored or sent anywhere. Close the tab and it is gone.
- Estimates, never diagnoses.Population figures describe groups. If sleep is affecting your days, talk to a clinician.