About CaffeineMath
CaffeineMath.com is a free tool that helps you understand exactly how caffeine moves through your body and how it affects your sleep. We built this calculator because most people dramatically underestimate how long caffeine stays active in their system.
Why We Built This Tool
Most caffeine calculators online are overly simple. They tell you caffeine has a 5 hour half-life and leave it there. But the reality is more nuanced. Your metabolism speed, whether you are pregnant, and the specific drinks you consume all affect how long caffeine stays in your system.
We wanted to build a tool that accounts for all of these variables and gives you a real, accurate picture of your caffeine levels throughout the day — not just a rough estimate.
The Science Behind Our Calculator
Our calculator is built on peer reviewed pharmacokinetic research. The core formula we use is the standard caffeine elimination equation used in clinical sleep research:
Remaining caffeine = Initial mg × (0.5 ^ (hours elapsed ÷ half-life))
This formula is used by researchers at institutions including UC Berkeley, Stanford, and the National Institutes of Health to model caffeine clearance in the human body.
Our Caffeine Data Sources
Every caffeine value in our drink list is sourced from published nutritional databases and manufacturer data. We update these values regularly to ensure accuracy. Our half-life values are based on the following research:
- Average half-life of 5 hours for healthy adults — based on multiple pharmacokinetic studies
- Slow metabolizer half-life of 8 hours — associated with CYP1A2 enzyme variants, oral contraceptives and certain medications
- Fast metabolizer half-life of 3 hours — associated with genetic CYP1A2 variants and smoking
- Pregnancy half-life of 12 hours — based on documented increases in caffeine half-life during pregnancy
Who This Tool Is For
CaffeineMath is for anyone who drinks caffeine and wants to sleep better. Whether you are a heavy coffee drinker struggling with poor sleep, someone who is newly sensitive to caffeine, or simply curious about the science — this tool gives you the information you need to make smarter decisions about when to have your last cup.
Our Commitment To Accuracy
We are committed to keeping our calculator accurate and up to date. If you notice any inaccurate caffeine values or have suggestions for improvements please contact us. We take data accuracy seriously because we know people rely on this tool to make decisions about their health.
Disclaimer
CaffeineMath.com is for informational purposes only and does not constitute medical advice. Individual caffeine metabolism varies significantly. Always consult your healthcare provider for personalized guidance especially if you are pregnant, taking medications or have an underlying health condition.
Contact Us
Have a question, suggestion or found an error? We would love to hear from you.
Email: hello.caffeinemath@gmail.com
Last updated: March 2026