Caffeine Half-Life Calculator

Understanding Caffeine Half-Life

Caffeine half-life is the time it takes for half of the caffeine in your system to be eliminated. The average half-life is approximately 5 hours, but individual variation ranges from 3 to 7 hours depending on genetics, age, and other factors ^[1].

Caffeine follows first-order elimination kinetics: the amount remaining at any time equals the initial dose × 0.5^(elapsed hours ÷ half-life). This means caffeine levels decline exponentially, not linearly ^[2].

Factors Affecting Half-Life

• Genetics: CYP1A2 enzyme variations can make individuals fast or slow caffeine metabolizers
• Age: Caffeine clearance may slow with age, leading to a longer half-life
• Habitual intake: Regular caffeine users may develop faster clearance over time
• Body composition: Larger individuals may metabolize caffeine at different rates

Use the half-life slider (3–7 hours) to explore how different metabolic rates affect your caffeine timeline throughout the day.

Multiple Dose Tracking

This calculator supports multiple caffeine intakes throughout the day. Each dose is tracked independently using the decay formula, and the total caffeine in your system at any hour is the sum of all active doses. This is useful for tracking morning coffee, afternoon tea, and pre-workout supplements.

For pre-workout caffeine timing, see our Pre-Workout Calculator.

How to Use This Calculator

1. Set your estimated caffeine half-life (default: 5 hours)
2. Enter your caffeine amount in milligrams (use the reference table below for common sources)
3. Set the hour of intake (0 = start of tracking period)
4. Add additional doses throughout the day if applicable
5. Click "Calculate Caffeine Levels" to see your 24-hour caffeine timeline

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