Caffeine & Metabolism Lab
Log your coffee, tea, or energy drinks and watch your caffeine level decay in real time. See exactly when you'll be ready to sleep — and when the crash is coming.
When can you sleep?
Log your first drink and watch your caffeine level decay in real time — across a live 24-hour curve.
The Caffeine & Metabolism Lab tracks your caffeine intake across multiple drinks and shows a live decay curve based on the 5.7-hour biological half-life. Log a coffee, an espresso, a green tea — the tool stacks all doses and shows your current caffeine level in milligrams, when the crash zone begins, and exactly when you'll have less than 50mg in your system and be ready to sleep.
How to Track Your Caffeine
- Select a beverage type and the time you drank it, then click Add Dose. Repeat for every caffeinated drink today.
- The decay curve appears immediately — showing your caffeine level across a 24-hour window with annotated zones: High Alert, Alert, and Sleep Ready.
- Check the stat cards for your current caffeine level, time until sleep-ready, and how many half-lives have elapsed.
Frequently Asked Questions
What is the caffeine half-life?
Caffeine's biological half-life averages 5.7 hours in healthy adults — meaning half of the caffeine you consume is eliminated every 5.7 hours. A 200mg dose at 8am leaves approximately 100mg at 1:42pm, 50mg at 7:24pm, and 25mg at 1:06am.
When is it safe to drink coffee before bed?
Most sleep researchers recommend stopping caffeine at least 6 hours before your intended sleep time. At the 50mg threshold (roughly one-fifth of a coffee), most people experience minimal impact on sleep onset and quality.
Why do some people feel caffeine less strongly?
Caffeine metabolism varies significantly by genetics (CYP1A2 enzyme variants), medication interactions, pregnancy, and habitual consumption. Slow metabolisers may have a half-life closer to 9–10 hours; fast metabolisers closer to 3–4 hours. This tool uses the population average of 5.7 hours.
Can caffeine stack from multiple drinks?
Yes — and this is one of the most underappreciated aspects of caffeine consumption. If you drink a coffee at 8am (95mg), an espresso at 11am (63mg), and a green tea at 2pm (30mg), all three are still contributing to your caffeine level at 6pm. This tool sums all active doses.