Caffeine Half-Life Calculator
Track remaining caffeine over time based on half-life dynamics.
This calculator provides educational estimates and does not replace guidance from a healthcare professional. Actual caffeine metabolism varies with genetics, medications, liver function, pregnancy, and smoking status. Always consult your clinician for personalized advice.
Table of Contents
How to Use
- Enter the initial amount of caffeine you consumed in milligrams.
- Provide the half-life to model (default values range from 3 to 7 hours for most adults).
- Specify how many hours have passed since intake.
- Optionally set a target threshold to learn when caffeine may drop below your preferred level, then click Calculate.
Understanding caffeine half-life
Half-life is the time required for the concentration of a substance in the body to decrease by half. Caffeine’s half-life typically ranges from 3 to 7 hours but can extend beyond 10 hours in pregnancy or for people with slower metabolism.
Factors that change caffeine metabolism
- Genetics and liver enzyme activity (CYP1A2).
- Medications such as oral contraceptives, SSRIs, or fluoroquinolones.
- Pregnancy, age, and hormonal changes.
- Smoking status—tobacco can shorten the half-life, while cessation lengthens it.
Frequently Asked Questions
- What half-life should I use?
- Most healthy adults metabolize caffeine with a half-life between 3 and 5 hours. If you are pregnant, taking medications, or sensitive to caffeine, consider using a longer half-life such as 6 to 8 hours.
- Does this calculator consider additional caffeine intake?
- No. The model assumes a single dose. If you consume more caffeine, run a new calculation and add the results to estimate your total remaining caffeine.
- Why is my actual experience different?
- Hydration, food intake, liver health, and genetics all influence caffeine clearance. Use this curve as a reference and adjust based on personal experience and professional advice.
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