Caffeine Half-Life Calculator
Calculate how much caffeine remains in your body over time.
See when caffeine levels drop low enough for a good night of sleep.
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Caffeine Remaining
Caffeine has a half-life of approximately 5 hours in healthy adults. This means every 5 hours, the amount in your body drops by half.
Core formula:
Remaining = Initial Amount × (0.5)^(Hours / Half-Life)
Common caffeine amounts:
| Beverage | Caffeine (mg) |
|---|---|
| Espresso shot | 63 mg |
| Drip coffee (8 oz / 240 mL) | 95 mg |
| Large coffee (16 oz / 475 mL) | 190 mg |
| Black tea (8 oz / 240 mL) | 47 mg |
| Green tea (8 oz / 240 mL) | 28 mg |
| Cola (12 oz / 355 mL) | 34 mg |
| Energy drink (8 oz / 240 mL) | 80 mg |
| Large energy drink (16 oz) | 160 mg |
Half-life variations:
- Healthy adults: 5 hours (range 3–7 hours)
- Smokers: ~3 hours (caffeine metabolized faster)
- Pregnancy: 9–11 hours (much slower elimination)
- Oral contraceptives: ~7 hours
Sleep recommendation:
- Caffeine below 50 mg is generally considered sleep-safe
- Avoid caffeine at least 6 hours before bedtime
- Some people are more sensitive and may need 8–10 hours
Safe daily limits:
- Adults: up to 400 mg per day
- Pregnant women: up to 200 mg per day