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Caffeine Half-Life Calculator

Track caffeine levels in your system over time with interactive charts and personalized sleep recommendations

Caffeine
Health
Calculator
Sleep

Personal Settings

2h5h8h

Average is 5-6 hours. Adjust based on your sensitivity.

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Current Status

Current Level:0.0mg
Sleep Safe:Yes

Caffeine Levels Over Time

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Understanding Caffeine Half-Life

Caffeine half-life is the time it takes for your body to eliminate half of the caffeine you've consumed. For most healthy adults, this is approximately 5-6 hours, but it can vary significantly between individuals.

This means if you drink a cup of coffee containing 100mg of caffeine at 2 PM:

  • At 7 PM (5 hours later): ~50mg remains in your system
  • At 12 AM (10 hours later): ~25mg remains
  • At 5 AM (15 hours later): ~12.5mg remains

The sleep-safe threshold of 25mg is based on research showing that caffeine levels below this amount typically don't significantly impact sleep quality for most people. However, individual sensitivity varies greatly.

Why this matters: Even if you don't feel the stimulating effects of caffeine, it can still interfere with your sleep architecture, reducing deep sleep and overall sleep quality.

Frequently Asked Questions (FAQ)

What is caffeine half-life and why does it matter?
Caffeine half-life is the time it takes for your body to eliminate half of the caffeine you consumed. The average is 5-6 hours, but it varies from 3-7 hours depending on factors like age, genetics, pregnancy, and medications. Understanding this helps you time your caffeine intake to avoid sleep disruption.
How does this calculator work?
The calculator uses the exponential decay formula C(t) = C₀ × (1/2)^(t/half-life) to track caffeine levels over time. It accounts for multiple caffeine doses throughout the day and shows when levels drop below 25mg - generally considered safe for sleep.
When should I stop drinking caffeine for better sleep?
Most people should avoid caffeine 6-8 hours before bedtime. However, this varies by individual. Use this calculator to find your personal cutoff time based on your caffeine sensitivity and typical consumption patterns.
What factors affect caffeine metabolism?
Caffeine half-life is influenced by age (slower in elderly), genetics (CYP1A2 enzyme variants), pregnancy (doubles half-life), medications (birth control, antibiotics), smoking (decreases half-life), and liver function. The 5-hour default is average for healthy adults.
Is this calculator medically accurate?
This calculator uses scientifically established pharmacokinetic principles and average values. However, individual responses vary significantly. It's designed for educational purposes and general guidance - consult healthcare providers for personalized advice.
How much caffeine is too much?
The FDA recommends no more than 400mg of caffeine daily for healthy adults (about 4 cups of coffee). Pregnant women should limit to 200mg. Individual tolerance varies - some people are more sensitive and should consume less.

Medical Disclaimer

This calculator is for educational and informational purposes only. It uses average pharmacokinetic values and should not be considered medical advice. Individual responses to caffeine vary significantly. Consult with healthcare professionals for personalized guidance, especially if you have medical conditions, take medications, or are pregnant or breastfeeding.