Half-Life Calculator
The Half-Life Calculator determines how much of a substance remains after a given time, based on its half-life — the time it takes for half the quantity to decay or be eliminated. Half-life applies to radioactive isotopes, medications in the body, environmental contaminants, and any exponential decay process.
How to Use This Calculator
- 1
Enter the initial amount of the substance.
- 2
Enter the half-life (use consistent time units — hours, days, years, etc.).
- 3
Enter the elapsed time in the same units.
- 4
Click Calculate to find the remaining quantity.
Frequently Asked Questions
Half-life (t½) is the time required for exactly half of a substance to decay or be eliminated. After one half-life: 50% remains. After two: 25%. After three: 12.5%. It follows exponential decay.