Caffeine Half-Life Calculator

How it works

Caffeine's half-life averages 5–6 hours but ranges from 2–12 hours depending on genetics, liver function, smoking status, and pregnancy. After one half-life, 50% remains; after two, 25%; after three, 12.5%. To have less than 10% remaining at bedtime, your last cup should be 3 half-lives before sleep. Oral contraceptives roughly double the half-life.