â Caffeine Calculator
When caffeine leaves your system & safe limits
How it works
Calculate how caffeine affects your body throughout the day. Enter your caffeine intake, body weight, and consumption time to see blood caffeine levels hour by hour. Find the latest safe time to drink coffee for good sleep. Based on caffeine's ~5-hour half-life.
Disclaimer: This calculator is for informational and educational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider.
Frequently Asked Questions
- How long before bed should I stop caffeine?
- At least 8-10 hours for most people. Caffeine has a half-life of about 5 hours, meaning half is still in your system after 5 hours. A coffee at 2 PM means ~50mg still circulating at midnight. Sensitivity varies â some people need even longer.
- How much caffeine is safe per day?
- Up to 400mg/day is considered safe for most adults (about 4 cups of coffee). Pregnant women should limit to 200mg/day. Teenagers should stay under 100mg/day. Individual tolerance varies significantly based on genetics and habitual use.