Caffeine Half-Life Calculator
Calculate how much caffeine remains in your body after a given time and get a bedtime recommendation.
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Caffeine Remaining
Caffeine half-life is approximately 5 hours in healthy adults:
Remaining Caffeine = Initial mg × (0.5 ^ (Hours Elapsed / 5))
Common caffeine amounts:
- Espresso shot: 63 mg
- Drip coffee (8 oz): 95 mg
- Large coffee (16 oz): 190 mg
- Black tea (8 oz): 47 mg
- Energy drink (8 oz): 80 mg
- Cola (12 oz): 34 mg
Sleep recommendation:
- Caffeine below 50 mg is generally safe for sleep
- Most experts recommend stopping caffeine 6–8 hours before bed
Factors affecting half-life:
- Pregnancy: half-life increases to 9–11 hours
- Smoking: half-life decreases to 3 hours
- Oral contraceptives: half-life increases to 5–10 hours