Caffeine Sensitivity Calculator
Estimate how long caffeine stays in your system based on your sensitivity.
Cup of coffee ≈ 95mg, espresso ≈ 65mg
Enter caffeine amount and time to calculate remaining caffeine.
This calculator estimates how much caffeine is still in your body at any given time after a drink, so you can judge whether it might interfere with your sleep.
Caffeine leaves the body gradually. On average it has a "half-life" of about 5–6 hours, meaning half of what you drank is still active 5–6 hours later. The calculator applies this steady decline based on your personal sensitivity and the time since your drink.
Because caffeine blocks the brain signals that make you feel sleepy, having too much still in your system at bedtime can make it harder to fall asleep and reduce deep sleep. A good rule of thumb is to stop caffeine at least 6 hours before bed.