Enter the initial quantity, final quantity, and total time passed to calculate the half-life. Half-life is defined as the time it takes for a value to decrease by half. This is most often used in nuclear physics.

## Half-Life Formula

So, how do you calculate half-life? Half-life is calculated using the exponential decay formulas, as shown below.

• Where N0 is the initial quantity
• N(t) is the quantity remaining after some time
• t1/2 is the half-life, and t is time.

This can be further simplified into the following to calculate half-life.

## What is half-life?

A half-life is the time it takes a given substance to deteriorate or lose half of its mass.

Half-life is a term mostly used in nuclear physics to describe the rate of decay of radioactive substances. As a result, the formula above includes the decay constant of the material. However, the half-life can also be calculated simply through time passed, initial quantity, and final quantity by re-arranging the very first equation above.

The idea of half-life is that since it’s exponential decay, it starts off losing a lot of mass to start, then slowly slows down. It will never actually reach absolute 0. Yet, of course, it would eventually approach an amount considered negligible.

## How to calculate a half-life?

How to calculate a half-life?

1. First, you must determine the initial quantity of your substance

For this example we will assume that to be 10 grams.

2. Next, you need to measure the time that has passed.

For this example we will assume 10 seconds.

3. Next, you need to measure the final quantity of substance

For this example we will assume 9 grams.

4. Finally, plug the needed information into the formula

79.84 is the half life.

## FAQ

What is a half life?

Half-life is the time it takes a given substance to deteriorate or lose half of its mass.