Half-Life Calculator (Radioactive)

Radioactive decay is the process by which unstable atoms lose energy over time — the Half-Life Calculator lets you solve for any unknown in that process. Select what you want to Solve For (Remaining Quantity, Half-Life, Time Elapsed, or Decay Constant), then enter your Initial Quantity, and the known values from Sample Parameters, Time Parameters, and Decay Properties to get the result alongside Percentage Remaining, Percentage Decayed, and Mean Lifetime.

Original amount of radioactive material

Current amount of radioactive material

Time that has passed since initial measurement

Time for half of the material to decay

Probability of decay per unit time

Results

Result

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Percentage Remaining

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Percentage Decayed

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Mean Lifetime

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Frequently Asked Questions

What is radioactive decay?

Radioactive decay is the process by which unstable atomic nuclei emit particles or electromagnetic radiation to become more stable. This process occurs randomly but at a predictable average rate for any given isotope.

What is half-life?

Half-life is the time required for exactly half of a radioactive substance to decay. It's a constant characteristic of each radioactive isotope and is independent of the initial amount of material.

How to calculate half-life?

Half-life can be calculated using the formula t₁/₂ = ln(2)/λ, where λ is the decay constant. Alternatively, if you know the initial and remaining quantities and time elapsed, you can use t₁/₂ = t × ln(2)/ln(N₀/N(t)).

What is the half-life of carbon-14?

Carbon-14 has a half-life of approximately 5,730 years. This makes it useful for dating organic materials up to about 50,000 years old through radiocarbon dating.

What is the half-life of uranium-238?

Uranium-238 has a half-life of about 4.47 billion years, making it one of the longest-lived radioactive isotopes. This extremely long half-life is why uranium can still be found naturally on Earth.

What is the difference between half-life and mean lifetime?

Mean lifetime is the average time a radioactive nucleus exists before decaying, calculated as 1/λ (where λ is the decay constant). It's related to half-life by the formula: mean lifetime = half-life / ln(2) ≈ 1.44 × half-life.

Can half-life be changed by external conditions?

No, half-life is an intrinsic property of each radioactive isotope and cannot be altered by external conditions like temperature, pressure, or chemical environment. It depends only on the nuclear structure of the atom.