Half-Life Calculator
Half-Life Calculator
Calculate remaining amounts, half-life durations, or elapsed time.
Result
0
What is Half-Life?
In science, half-life is the time required for a quantity to reduce to half of its initial value. It is most commonly used in nuclear physics to describe how quickly unstable atoms undergo radioactive decay, but it is also widely used in pharmacology to determine how long a drug stays active in the human body.
Half-Life Formula
The standard mathematical equation for calculating radioactive decay or biological half-life is:
$$N(t) = N_0 \cdot (0.5)^{\frac{t}{h}}$$
Where:
$N(t)$ = Remaining amount after time $t$
$N_0$ = Initial amount
$t$ = Elapsed time
$h$ = Half-life duration
Frequently Asked Questions
What happens after two half-lives?
After one half-life, 50% of the original substance remains. After two half-lives, half of that 50% decays, leaving exactly 25% of the original amount. After three half-lives, 12.5% remains, and the pattern continues exponentially.
Can I use any time unit?
Yes! As long as you use the exact same unit for both the Half-Life and the Elapsed Time (e.g., both in days, both in hours, or both in years), the calculator will provide mathematically accurate results.