HES100 · HEALTHFUL LIVING

Caffeine & Bedtime Explorer

Explore how caffeine amount and timing change the estimated amount remaining at bedtime.

Set up your example

Starter example: 200 milligrams (mg) at 1 PM, bedtime at 11 PM. This is an illustrative amount, not a standard drink size.

Enter drinks from one calendar day. Choose “Next day” for a bedtime such as 1 AM.

Estimated caffeine at bedtime

Five-hour half-life means half the caffeine remains after 5 hours, one-quarter after 10 hours.

This teaching model estimates caffeine remaining, not blood concentration or how well you will sleep. People metabolize caffeine differently; product caffeine amounts also vary.

Model and evidence

For each drink: remaining caffeine = amount × 0.5(hours elapsed ÷ 5). The tool adds the remaining amounts from all entered drinks. It assumes immediate absorption and a fixed five-hour half-life; it excludes earlier days, absorption delays, and individual differences.

The National Academies’ Pharmacology of Caffeine describes first-order elimination, an average half-life around five hours, and substantial variation.

Your entries stay in this browser page and are not submitted to your instructor. This tool does not save them; reloading starts over.