# How do you calculate half life of carbon 14?

##### 1 Answer

You can calculate half life if you know how much of the substance is left after a certain time, though typically it works the other way - the half life is known, and used to calculate age.

#### Explanation:

The formula for half life calculations is:

or

or

Where

Half life is defined as the time after which half of a sample of a radioactive material will have decayed. In other words, if you start with 1 kg of material with a half life of 1 year, then after 1 year you will have 500g. After another year you will have half of that, or 250 g. After another year, you will have 125 g, and so on.

Calculating

Calculating the half life from

The formula is also frequently expressed using the natural logorithm:

So, to answer the question, in order to calculate the half life of

If, however, your goal is to determine the half life of carbon so you can use it to determine an age, then Google is your friend:

5730 years.