Half Life: What It Calculates

Half Life applies a scientific relationship to the quantities entered. Units are part of the calculation, so they should match the form expected by the formula.

The Formula or Method

Half-life decay follows N = N0(1/2)^(t/t½), where t½ is the half-life.

Scientific relationship

The result follows the physical, chemical, or scientific relationship stated above. Keep units compatible with that relationship before interpreting the output.

Using Half Life

Enter each measurement with the unit expected by the calculator. Convert quantities first when necessary so that the formula is not combining incompatible units.

1. Identify the quantities required by the scientific relationship.
2. Convert units if the formula requires a common unit system.
3. Enter the measurements and calculate the result.
4. Check units and order of magnitude before interpreting it.

Worked Example

After 3 half-lives, 12.5% of the original quantity remains.

Checking the Result

Scientific results are only as reliable as the measurements and assumptions supplied. Experimental uncertainty, calibration, dilution, temperature, pressure, and unit conventions can affect the final value depending on the tool.