Health
Caffeine Half-Life & Sleep Impact Calculator
How much caffeine is still in your system — and your ideal cutoff time.
Caffeine half-life: 5 hours average
Caffeine's half-life is 5 hours in healthy adults (range: 3–7 hours). A 200mg coffee at noon → 100mg at 5pm → 50mg at 10pm. At 50mg, most people can sleep — but sleep quality may still be impaired.
Common caffeine amounts
- Espresso (1 shot): 63mg
- Drip coffee (8oz): 95mg
- Red Bull (8.4oz): 80mg
- Monster (16oz): 160mg
- Matcha (8oz): 70mg
⚡ CalcWolf Insight
A 2-pm coffee still has 50mg of caffeine in your system at 11pm for an average metabolizer. Light sleepers may feel effects at even lower levels. Genetics (CYP1A2 gene) cause 2–3× variance in metabolism speed.
Frequently asked questions
When should I stop drinking coffee before bed?▾
For 8pm bedtime, cut off by 1–2pm for an average metabolizer. If you're a slow caffeine metabolizer (the "coffee doesn't affect me" feeling is a myth), cut off by noon.
How long does caffeine stay in your system?▾
Caffeine half-life averages 5-6 hours. A coffee at 2 PM means roughly half the caffeine is still in your blood at 8 PM. After 5 half-lives (25-30 hours), 97% is eliminated. This is why sleep experts recommend a caffeine cutoff of 2 PM or earlier.
✓ Math logic verified against primary sources
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