💊 Drug Half-Life Calculator
Estimate how much of a dose remains in the body after a given amount of time, based on the drug’s half-life.
What drug half-life means
A drug’s half-life is the time it takes for the amount of the drug in the body to reduce by half, assuming standard first-order elimination kinetics, which applies to most medications at typical doses.
The formula used
This calculator uses the standard exponential decay formula: Remaining Amount = Initial Dose × 0.5^(Elapsed Time ÷ Half-Life). It also reports the percentage of the original dose remaining and how many half-lives have passed.
This is a general reference calculation for educational purposes. Actual drug clearance in the body can be affected by individual metabolism, organ function, drug interactions, and formulation, so this tool does not replace guidance from a licensed healthcare professional or pharmacist.