Use Activity Decay Calculator when you need to compute the radioactive activity after a time as A = A₀·e^(−λt) with λ = ln2/t½. Enter Initial activity, Half-life, and Elapsed time using the definitions and units below so the result can be reproduced.

Initial activity

Initial activity A₀.

Half-life

Half-life of the nuclide; must be greater than zero.

Elapsed time

Elapsed time since the initial measurement.

The published tool contract uses this rule: Compute the radioactive activity after a time as A = A₀·e^(−λt) with λ = ln2/t½.

Activity

Activity after the elapsed time.

The calculation does not propagate measurement uncertainty, sampling error, or biological and chemical variability.

Retain the original Initial activity, Half-life, and Elapsed time values and their units alongside the result. Decay Remaining Calculator is useful when you instead need to compute the remaining amount after radioactive decay as N = N₀·(1/2)^(t/t½). Specific Activity Calculator provides another view by helping you compute the specific activity of a radioactive sample as activity divided by sample mass.

• Decay Remaining Calculator

  Compute the remaining amount after radioactive decay as N = N₀·(1/2)^(t/t½).

• Specific Activity Calculator

  Compute the specific activity of a radioactive sample as activity divided by sample mass.

• Decay Half-Life Calculator

  Solve the half-life from an initial amount, a remaining amount, and the elapsed time as t½ = t·ln2 / ln(N₀/N).