Calculate
Half-Life Formulas
The amount of substance remaining after time t:
N(t) = N0 x (1/2)^(t / t1/2)The decay constant (lambda):
lambda = ln(2) / t1/2 = 0.693 / t1/2Time to reach a given remaining amount:
t = t1/2 x log2(N0 / N)Common Radioactive Isotopes
| Isotope | Half-Life | Use / Significance |
|---|---|---|
| Carbon-14 | 5,730 years | Radiocarbon dating |
| Uranium-238 | 4.5 billion years | Rock dating, nuclear fuel |
| Radium-226 | 1,600 years | Radiation therapy (historical) |
| Iodine-131 | 8.02 days | Thyroid treatment |
| Cesium-137 | 30.17 years | Nuclear fallout marker |
| Tritium (H-3) | 12.3 years | Watch dials, fusion research |
| Cobalt-60 | 5.27 years | Medical sterilization |
| Polonium-210 | 138 days | Static eliminator |
Privacy & Limitations
- All calculations run entirely in your browser -- nothing is sent to any server.
- Results are computed using standard formulas and should be verified for critical applications.
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Half-Life Calculator FAQ
What is Half-Life Calculator?
Half-Life Calculator is a free engineering & physics tool that helps you Calculate radioactive decay, remaining quantity, and elapsed half-lives.
How do I use Half-Life Calculator?
Enter your input values, review the calculated output, and adjust inputs until you reach the result you need. The result updates in your browser.
Is Half-Life Calculator private?
Yes. Calculations run locally in your browser. Inputs are not uploaded to a server by default, and refreshing the page clears session data.
Does Half-Life Calculator require an account or installation?
No. You can use this tool directly in your browser without sign-up or software installation.
How accurate are results from Half-Life Calculator?
This tool applies standard formulas or deterministic processing logic for estimates. For medical, legal, tax, or investment decisions, verify with a qualified professional.
Can I save or share outputs from Half-Life Calculator?
You can bookmark this page and copy outputs manually. Results are not persisted in your account and are typically not embedded in the URL.