Caffeine reaches peak levels in your blood 30-60 minutes after consumption.
Select beverages from the list and set quantities to calculate total daily caffeine intake.
See if your intake is within FDA-recommended safe limits with color-coded indicators.
Use the timer mode to see how caffeine levels decrease over time using half-life calculation.
Find out when caffeine drops below the 50mg sleep threshold so you know when to stop.
Caffeine follows first-order elimination kinetics with an average half-life of 5.7 hours in healthy adults. This means roughly half the caffeine is eliminated every 5.7 hours. The half-life can range from 3-7 hours depending on genetics, liver function, and pregnancy status.
C(t) = C₀ × 0.5^(t / 5.7)
The FDA recommends a maximum of 400mg of caffeine per day for healthy adults
Pregnant women should limit caffeine to 200mg per day according to ACOG guidelines
Caffeine has an average half-life of 5.7 hours but varies from 3-7 hours between individuals
Stop consuming caffeine at least 6 hours before bedtime for better sleep quality
Caffeine takes 30-60 minutes to reach peak levels in your bloodstream after consumption
Genetics play a major role in caffeine metabolism - some people are fast or slow metabolizers
Green tea has less caffeine than coffee but contains L-theanine which promotes calm alertness
Decaf coffee still contains 2-15mg of caffeine per cup
Our free caffeine calculator helps you track daily caffeine intake from coffee, tea, energy drinks, and more. Calculate how long caffeine stays in your system using the half-life decay formula, and check whether you're within FDA-recommended safe limits.
Add up the caffeine content of all beverages consumed throughout the day. A standard cup of drip coffee has ~95mg, espresso ~63mg, black tea ~47mg, and green tea ~28mg. Energy drinks vary from 80-300mg. Compare your total against the FDA recommended maximum of 400mg for healthy adults.
Caffeine follows exponential decay with an average half-life of 5.7 hours. The formula C(t) = C₀ × 0.5^(t/5.7) calculates remaining caffeine at any time. This means 200mg of caffeine at 8 AM becomes ~100mg by 1:42 PM and ~50mg by 7:24 PM. Individual variation ranges from 3-7 hours.
ACOG recommends limiting caffeine to 200mg per day during pregnancy. Caffeine half-life doubles during pregnancy (up to 11+ hours), meaning it stays in the system much longer. This calculator includes a pregnancy mode with adjusted safe limits and extended half-life calculations.
Research shows caffeine consumed within 6 hours of bedtime significantly reduces sleep quality. Our calculator determines when caffeine drops below the 50mg sleep threshold, helping you plan your last caffeinated drink of the day for optimal sleep.
Data sourced from trusted institutions
All formulas verified against official standards.