Caffeine Half-Life Calculator
Find out how much caffeine is still in your system hours after your coffee. Plan your last cup for better sleep. Free tool.
Average half-life is about 5 hours, ranging from 2-10 hours depending on genetics, pregnancy and medication.
Frequently asked questions
- How long does caffeine last?
- Half of it is gone after about 5 hours, a quarter after 10 hours. A quarter can still affect sleep 12 hours later.
- How much caffeine is in coffee?
- Roughly 95 mg per 8 oz brewed coffee, 45 mg per espresso shot, 45 mg per black tea, 30 mg per cola.
- When should I have my last coffee?
- At least 6 hours before bed, or when your remaining caffeine drops under about 50 mg.
- Why does caffeine affect me differently?
- Genetics, liver enzymes, pregnancy, oral contraceptives and smoking all change how fast you clear caffeine.
This tool runs entirely in your browser. No data is uploaded anywhere.