Free tools
Six calculators and quizzes, free and without signup. Each one answers its question in seconds with arithmetic you can check by hand, then points you at the guide behind it.
Arithmetic you can check: every formula, in full →CALCULATOR
Caffeine half-life calculator
How many mg will still be in your blood at bedtime? Dial in your last cup, dose and metabolism.
CALCULATOR
Sleep cycle calculator
The best bedtimes for your wake-up time - land at the end of a 90-minute cycle, not the groggy middle.
CALCULATOR
Sleep debt calculator
Your last seven nights, the damage, and an honest repayment plan.
QUIZ · 2 MIN
Why am I tired?
Nine taps rank your likeliest culprits and hand you the right 14-day test to run first.
QUIZ · 90 SEC
Chronotype quiz: owl or lark?
Eight questions give your natural wake time, bedtime and peak focus window.
CALCULATOR
Water intake calculator
A realistic daily target from your weight, activity and climate - and the truth about the 8-glasses rule.