Half-life calculator
The amount remaining after a given time, or the age of a sample (carbon-14 dating).
How it works
N(t) = N0 × (1/2)^(t / T½). Age = T½ × log₂(N0 / N). Carbon-14 has a half-life of 5,730 years.
Results are for guidance only and do not replace professional advice.
Worked example
With the default values:
- Initial amount100
- Half-life5730
- Time elapsed (same unit)10000
you get:
- Amount remaining29.829244 (29.829 %)
- Half-lives elapsed1.745
- Decay constant λ1.2097 × 10^-4
Frequently asked questions
How does the “Half-life calculator” tool work?
N(t) = N0 × (1/2)^(t / T½). Age = T½ × log₂(N0 / N). Carbon-14 has a half-life of 5,730 years.
What do I need to enter?
Just fill in: initial amount, half-life, time elapsed, or: percentage left. The result updates as you type.
Can you give an example?
Initial amount: 100; Half-life: 5730; Time elapsed (same unit): 10000 → Amount remaining: 29.829244 (29.829 %); Half-lives elapsed: 1.745.
Is this calculator free, and is my data private?
Yes. HOD Calc is completely free with no sign-up. The calculation runs in your browser: nothing you type is sent or stored.