The formula

For every recorded drinkremaining = intake × ½(elapsed hours ÷ half-life hours)

CaffOut calculates that value for each drink, then adds the results. A 100 mg drink logged one configured half-life ago contributes an estimated 50 mg. Two half-lives later, it contributes an estimated 25 mg.

What goes into the estimate

  • The caffeine amount attached to each recorded drink.
  • The time you recorded drinking it.
  • The estimated half-life configured in your CaffOut settings.

If a drink's caffeine amount is unknown, CaffOut keeps the record visibly incomplete rather than inventing a value.

Why this is an estimate

Caffeine pharmacokinetics vary between people and circumstances. A systematic analysis covering 141 publications examined differences associated with factors including smoking, oral contraceptives, medications, and disease. The FDA also notes wide variation in caffeine sensitivity and elimination speed.

Systematic analysis of caffeine pharmacokinetics (peer-reviewed, 2022)FDA: Spilling the Beans — How Much Caffeine is Too Much?

What CaffOut does not claim

CaffOut does not monitor your body in real time, determine blood caffeine concentration, diagnose a condition, calculate a guaranteed “safe sleep” time, or provide medical advice. If caffeine is affecting your health, pregnancy, medication, or sleep, talk with a qualified health professional.