Caffeine Half-Life Calculator
Predict how much caffeine is in your system over time.
Uses a 5-hour half-life, the average for healthy adults. Yours can run anywhere from 1.5 to 9.5 hours based on genetics, pregnancy, smoking, and certain medications. Sleep researchers suggest staying under 100 mg in the 6 hours before bed.
About
Caffeine half-life is roughly 5 hours. The 200mg coffee at 3pm still has 100mg in you at 8pm. This calculator graphs your active caffeine load throughout the day from your drinks.
How to use
- Add each drink with its caffeine amount and time.
- Set your bedtime.
- See the caffeine level curve and how much is left at bedtime.
FAQ
What's a safe level for sleep?+
Most people need under 50mg in their system to fall asleep easily. Some need under 20mg. The Sleep Foundation recommends no caffeine within 6 hours of bed.
Why is my half-life different?+
Genetics (CYP1A2 variants), pregnancy, smoking, and some medications change caffeine metabolism. Some people clear it in 3 hours, others take 8.