Caffeine Half-Life Calculator

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Caffeine Half-Life Calculator

Calculate residual caffeine at bedtime from your drinks and metabolism

Metabolism profile

Drinks consumed today

Residual caffeine at bedtime —
Sleep impact —
Recommended last drink by —

Caffeine decay over 12 hours

Chart will appear once you log drinks

Today's total caffeine — —

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We use first-order exponential decay (Drake et al. 2013, Journal of Clinical Sleep Medicine): residual caffeine at bedtime equals the sum across all drinks of (initial mg × 0.5 ^ (hours_elapsed / half_life)). The half-life varies by metabolism profile — normal adults average ~5 hours; smokers clear caffeine ~40% faster via CYP1A2 induction; pregnant women retain caffeine 2× longer; OCP users and people with liver impairment process it more slowly. Genetic CYP1A2 variants also shift the half-life by ~30%. The FDA recommends keeping daily intake below 400 mg (200 mg during pregnancy). The recommended cutoff time walks backward from bedtime in 5-minute steps, finding the latest drink time that keeps residual caffeine at or below your chosen sleep-impact threshold.

This tool is for educational purposes only. Individual caffeine metabolism varies. For chronic sleep issues, consult a doctor.

See also: Sleep Cycle Calculator, Water Intake Calculator, Cron Expression Generator (cutoff reminders).

Caffeine Half-Life Calculator

Calculate residual caffeine at bedtime from your drinks and metabolism profile. Find your optimal cutoff time to avoid sleep disruption. 7 metabolism profiles + 11 common drinks, all local.

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