Half-Life Calculator

What a half-life curve shows

A compound's half-life is the time it takes for the amount present to fall by half. After one half-life 50% remains, after two 25%, after three 12.5%, and so on. Because each step halves what is left, the curve falls quickly at first and then flattens — it never quite reaches zero, but after five half-lives less than 4% remains.

What the calculator does

Enter the half-life, an amount, and how often it is added. The chart plots the amount remaining over time, adding each new amount on top of what is left from earlier ones. With repeated additions the peaks climb until the amount cleared between additions equals the amount added; that plateau is called steady state, and it is reached after roughly four to five half-lives regardless of the amount.

Reading the results

• Peak — the highest point just after an addition.
• Trough — the lowest point just before the next addition.
• Time to steady state — how long until peaks and troughs stop climbing.

A shorter interval relative to the half-life gives a flatter line with a higher plateau; a longer interval gives bigger swings between peak and trough.

Assumptions

The model assumes first-order elimination (a constant fraction cleared per unit time) and instant absorption. Real-world behaviour depends on many factors the model ignores, so treat the output as an illustration of the maths, not a prediction.

Working from a powder? The reconstitution calculator converts vial amount and water volume into a measured draw. This tool is for educational and research purposes and does not provide medical advice.