ONE FORMULA, ONE ANSWER
Radioactive Activity Decay Calculator
Calculate activity decay of a single nuclide with a constant decay rate. Choose input units and calculate one value within the stated conditions.
Inputs
Calculations run in this browser. Scientific notation such as 1.2e-3 is supported. Do not group thousands.
Result
Remaining activity A
Enter values and select Calculate.
A = A₀ exp(−λt)
Assumptions
Required: A₀,t≥0, λ>0 for independent exponential decay of one nuclide. Daughter growth, decay chains, detector efficiency and radiation dose are excluded. Numeric underflow is not reported as physical extinction.
Displayed values are floating-point approximations. Design safety factors and unprovided error contributions are not calculated.
Formula references and credits
NaNa Lab created the code, descriptions, icons and preview images. Text, figures and code from the linked references have not been reproduced.
Physical constants: NIST / CODATA 2022. The values of μ₀ and ε₀ are measured recommendations, not exact defining constants. Values and precision notes are in the source record.
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