How to use it
- Add each caffeinated drink with the time you had it.
- Adjust the amount if you know it.
- Enter your bedtime and, optionally, change the half-life assumption.
- Review the estimate and decay chart.
Understanding your results
We use a simple exponential model: after one half-life, about half the caffeine remains. The default half-life is 5 hours, a commonly cited average, but real values vary widely (roughly 2–10 hours) with genetics, pregnancy, medications, smoking and more.
A practical cutoff
Many people find that avoiding caffeine for 6–8 hours before bed helps. If you're sensitive to caffeine, an earlier cutoff may suit you better.