I love coffee, but I hated the guessing game that starts every afternoon: “If I grab another cup, will it wreck my sleep?” Existing “caffeine trackers” felt clunky—too many taps, gimmicky gamification, sketchy data sharing. I wanted a one-screen, science-backed calculator that shows, in seconds, exactly how much caffeine will still be in your system—and when you’ll be in the clear. What’s new & unique Personalized half-life engine – We let you adjust for age, pregnancy, smoking status, and even common medications that slow/accelerate caffeine metabolism. Most tools assume everyone has the same 5-hour curve (spoiler: we don’t!). Real-time decay graph – Every input instantly redraws the curve so you can see your caffeine level hour-by-hour, not just read a table. Zero-tracking, zero sign-up – Everything runs client-side; nothing leaves your browser. Your late-night espresso secrets stay yours. Accessible everywhere – Pure HTML/CSS/JS, Lighthouse-optimized → loads fast on flaky café Wi-Fi and works great in dark mode. What we’re most proud of We distilled a pile of peer-reviewed pharmacokinetic studies into an interface your sleepy brain can use at midnight. Early beta testers say it finally helped them push that last cup earlier—and get better sleep without giving up coffee. Try it, play with the sliders, and let us know what surprises you! ☕⚡

Caffeine Half-Life Calculator

Calculate how long caffeine stays in your system

Calculate how long caffeine stays in your system