Caffeine Half-Life & Sleep Window Calculator
Model the exponential decay of caffeine in your bloodstream. Track active clearance curves, compare fast vs. slow metabolic rates, and map your safe sleep latency window.
☕ Caffeine Intake & Metrics
🔬 Sleep Window & Clearance
The Science of Caffeine Half-Life & Sleep Latency
How does caffeine decay work in the body?
Caffeine has an average **biological half-life of 5 hours**, but this metabolic rate varies widely (ranging from 3 to 10 hours) based on genetics (the **CYP1A2** liver enzyme gene), age, pregnancy status, smoking habits, and liver health. If you ingest 200mg of caffeine, 100mg remains active after one half-life (5 hours), 50mg remains after two half-lives (10 hours), and so on.
Why is 50mg the sleep latency limit?
Caffeine acts as an **adenosine receptor antagonist**, binding to adenosine receptors in the brain to block the accumulation of natural "sleep pressure". Clinical sleep studies indicate that when active caffeine in your bloodstream exceeds **50mg**, it blocks enough adenosine receptors to increase sleep latency (difficulty falling asleep) and significantly disrupt slow-wave deep sleep cycles.
Optimizing your caffeine curfew window
To ensure deep rest, establish a **caffeine curfew** based on your metabolic rate. For a standard 5-hour half-life, a 150mg cup of coffee taken at 12:00 PM will decay to approximately 37mg by a 10:00 PM bedtime, rendering it safe. However, taking that same cup at 3:00 PM leaves over 75mg at bedtime, which will likely delay and fragment your sleep.