Caffeine half-life averages ~5 hours
HighClinical pharmacology puts the elimination half-life of caffeine near 5 hours in a typical healthy adult. It varies widely by person: smoking speeds it up (~3 hours, via CYP1A2 induction), while pregnancy and oral contraceptives slow it down (often past 10 hours). The slider lets you model your own rate across that 2–12 hour range.
StatPearls — Caffeine pharmacology (NCBI Bookshelf NBK223808) ↗