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Calculate initial quantity, half-life, elapsed time and final quantity

How to use the half-life calculator

This calculator lets you calculate the following:

  • What quantity is left, given an initial quantity, the half-life and the elapsed time.
  • How long it takes to reach a certain value, given an initial quantity and the half-life.
  • What half-life is needed to reach a certain quantity in a certain time, given an initial quantity.
  • What initial amount is needed ti reach a certain quantity after a certain time, give the half-life.

Select the variable you'd like to calculate

The half-life is the time it takes for a quantity to decrease to half of its original size. The term is frequently used when making calculations related to radioactive decay.

Read more about half-life here: