Caffeine Sensitivity Calculator
Estimate how long caffeine stays in your system based on your sensitivity.
Calculator
Cup of coffee ≈ 95mg, espresso ≈ 65mg, black tea ≈ 47mg.
Estimated Remaining in System
Enter a caffeine amount and the time you drank it to estimate how much is left.
About the Caffeine Calculator
This calculator estimates how much caffeine is still in your body after a drink, so you can judge whether it might interfere with your sleep tonight.
Caffeine leaves the body gradually. It has a half-life of roughly 4–6 hours depending on your sensitivity, meaning half of what you drank is still active that many hours later. The tool applies this steady decline from the time of your drink.
Because caffeine blocks the brain signals that make you feel sleepy, having too much in your system at bedtime can delay sleep and reduce deep sleep. A common guideline is to stop caffeine at least 6 hours before bed.