Radioactive Half-Life Calculator
Remaining quantity after radioactive decay.
Enter your values
ⓘ Live results
Results
- Remaining quantity
- 29.8292 g
- Fraction remaining
- 29.829%
- Decay constant
- 1.2097e-4 per year
- Half-lives elapsed
- 1.75
Quick answer
N = N0 x 0.5^(t/half-life).
N = N0 (1/2)^(t/T)
How to use the Radioactive Half-Life Calculator
- 1Enter the initial quantity and the substance's half-life (5,730 years for carbon-14).
- 2Enter the elapsed time in the same units as the half-life.
- 3Read the remaining quantity and fraction left.
Worked example
Using the values the calculator loads with:
Inputs
- Initial quantity100 g
- Half-life5730 years
- Elapsed time10000 years
Results
- Remaining quantity29.8292 g
- Fraction remaining29.829%
- Decay constant1.2097e-4 per year
- Half-lives elapsed1.75
Frequently asked questions
What is carbon dating based on?
Comparing the remaining carbon-14 fraction in organic remains to estimate age using this formula.
Does half-life depend on amount?
No — half-life is constant regardless of how much material is present.
About this calculator
- Built and reviewed by James Whitfield · How we build and test calculators
- Report an error
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.