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Note: Results are estimates based on average metabolism. Individual results may vary.
Based on 5-hour half-life • 24 hours from consumption
Find answers to common questions about caffeine, sleep, and our calculator
Caffeine half-life is the time it takes for half of the caffeine in your system to be metabolized. The average half-life is approximately 5 hours, meaning if you consume 100mg of caffeine, about 50mg will remain after 5 hours, and 25mg after 10 hours.
Caffeine blocks adenosine receptors in your brain. Adenosine is a neurotransmitter that promotes sleepiness and deep sleep. By blocking these receptors, caffeine prevents the natural sleep pressure from building up, making it harder to fall asleep and reducing deep sleep quality.
Our calculator uses the standard 5-hour half-life formula, which is accurate for most healthy adults. However, individual metabolism can vary based on genetics, age, medications, and other factors. Use this as a guideline and adjust based on your personal experience.
The calculator shows the remaining caffeine from a single drink. If you consume multiple drinks, add their caffeine amounts together and use that total. Remember that caffeine accumulates, so multiple drinks throughout the day will result in higher total caffeine levels.
Yes, decaf coffee typically contains 2-5mg of caffeine per 8-ounce cup, compared to 95mg in regular coffee. While this is a 95% reduction, it's not completely caffeine-free. For most people, this small amount won't significantly affect sleep, but if you're highly sensitive, consider avoiding it 4-6 hours before bed.
Tolerance affects how you "feel" caffeine's effects, but it doesn't change how quickly your body metabolizes it. Even with tolerance, caffeine still disrupts sleep architecture. The calculator shows the actual caffeine remaining in your system, regardless of tolerance level.