Enter the parent isotope amount, daughter isotope amount, and half-life into the calculator to determine the absolute age of a sample.

Absolute Age Calculator

Enter the daughter-to-parent isotope ratio measured in your sample.

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Absolute Age Formula

The following formula is used to calculate the absolute age of a sample given the parent isotope amount, daughter isotope amount, and half-life.

t = \frac{T_{1/2} \cdot log(1 + \frac{D}{P})}{log(2)}

Variables:

  • t is the absolute age of the sample (years)
  • T1/2 is the half-life of the parent isotope (years)
  • D is the amount of daughter isotope
  • P is the amount of parent isotope

To calculate the absolute age, multiply the half-life by the natural logarithm of 1 plus the ratio of the daughter isotope to the parent isotope. Then, divide the result by the natural logarithm of 2.

What is Absolute Age?

Absolute age is a measure of the actual age of a geological or archaeological sample in years. Unlike relative age, which only determines the order of events, absolute age provides a quantifiable age. This is typically determined through radiometric dating methods, which measure the decay of radioactive isotopes within the sample. By knowing the half-life of the parent isotope and the ratio of parent to daughter isotopes, scientists can calculate the time that has elapsed since the sample formed.

How to Calculate Absolute Age?

The following steps outline how to calculate the Absolute Age.

  1. First, determine the amount of parent isotope (P) in the sample.
  2. Next, determine the amount of daughter isotope (D) in the sample.
  3. Next, determine the half-life (T1/2) of the parent isotope.
  4. Finally, calculate the absolute age (t) using the formula provided above.
  5. After inserting the values and calculating the result, check your answer with the calculator above.

Example Problem : 

Use the following variables as an example problem to test your knowledge.

Parent Isotope Amount (P) = 50 units

Daughter Isotope Amount (D) = 150 units

Half-Life (T1/2) = 1,000 years