Half Life Calculator
Calculate remaining quantity, decayed amount, and percentage left based on half-life and elapsed time.
Result
Remaining Quantity
Decayed Amount
Percentage Remaining
Number of Half-Lives
What is a Half Life Calculator?
A half life calculator determines how much of a substance remains after a given time based on its half-life—the time required for half of the substance to decay. It is widely used in physics, chemistry, medicine, and archaeology.
How to Use
- Enter the initial quantity of the substance.
- Input the half-life value and select its time unit.
- Input the elapsed time and select its time unit.
- Click Calculate to see remaining quantity, decayed amount, percentage left, and number of half-lives.
Frequently Asked Questions
What is half-life?
Half-life is the time required for half of a radioactive substance to decay into a different element or isotope.
Can I use different units for half-life and elapsed time?
Yes, this calculator supports independent unit selection for half-life and elapsed time, automatically converting them.
What formula does this calculator use?
It uses the exponential decay formula: remaining = initial × (0.5)^(elapsed / halfLife).
Is this calculator free?
Yes, BestCalc calculators are completely free and run locally in your browser.