How caffeine builds up and fades
Caffeine doesn’t leave your body all at once — it decays gradually, and the commonly cited average half-life is about 5 hours, meaning roughly half of it clears every 5 hours. Drinking more coffee, or coffee with a higher caffeine content, raises your peak amount and stretches out the time until it’s mostly gone.
How this calculator works
Enter how many cups you’ve had, the estimated caffeine per cup (drip coffee averages around 95 mg per 8 oz cup, though this varies widely by brew strength), and your body weight. The calculator totals your caffeine intake, expresses it relative to your body weight, and estimates how many hours it would take — using the 5-hour half-life — for your caffeine level to decay to a low, largely unnoticeable amount (about 25 mg).
Note: Caffeine sensitivity and metabolism vary a lot between individuals due to genetics, tolerance, medication, and other factors. This tool is for general educational and planning purposes only and is not medical advice.