Half-Life Calculator
Use this half-life calculator to estimate how much material remains after a certain time, how much has decayed, and how many half-lives have passed.
Half-Life Result
Understanding Half-Life
Half-life is the time it takes for half of a substance to decay, reduce, or transform. It is most commonly used for radioactive materials, but the same idea can also appear in medicine, chemistry, and environmental science.
If a material has a half-life of 10 years, then after 10 years half remains. After 20 years, one quarter remains. After 30 years, one eighth remains.
How Half-Life Works
Half-life decay follows a repeating pattern. Each half-life reduces the remaining amount by 50%, not by a fixed number.
| Half-Lives Passed | Amount Remaining | Amount Decayed |
|---|---|---|
| 1 | 50% | 50% |
| 2 | 25% | 75% |
| 3 | 12.5% | 87.5% |
| 4 | 6.25% | 93.75% |
| 5 | 3.13% | 96.87% |
Why Half-Life Is Important
Half-life helps scientists estimate how materials change over time. In geology and archaeology, half-life is used in dating methods such as carbon-14 dating and radiometric dating.
In medicine, half-life helps explain how long a substance remains active in the body. In nuclear science, it helps estimate how long radioactive material may remain detectable.
Half-Life Calculator FAQ
What is half-life?
Half-life is the time required for half of a substance to decay, reduce, or transform.
What happens after one half-life?
After one half-life, 50% of the original amount remains and 50% has decayed.
What happens after two half-lives?
After two half-lives, 25% of the original amount remains and 75% has decayed.
Can half-life be used for carbon dating?
Yes. Carbon-14 dating uses the half-life of carbon-14 to estimate the age of once-living organic material.
Does a radioactive material become zero after many half-lives?
Mathematically, the amount keeps getting smaller. In real measurements, detection limits also matter.