Percent Change Calculator

How to use this calculator

Enter Earlier value, Later value. The result updates in your browser as you edit an input. The prefilled values are examples only.

How the estimate works

Divide the difference between later and earlier values by the earlier value.

What can change the answer?

Percentage change is undefined when the earlier value is zero. Use a consistent definition and measurement period for both figures.

Before relying on the result

Check that both figures describe the intended geographic boundary and reference period. Confirm units, source definitions and any uncertainty information in the original dataset. The calculator does not independently verify those details or explain the causes of a change.

Further reference

For source data or a more detailed method, see U.S. Census Bureau: QuickFacts. The calculator does not automatically import data from this source.

Worked example with the default inputs

A figure moving from 100 to 115 increases by 15, or 15%. Reversing the comparison gives a decrease of about 13.04%, because the denominator then becomes 115.

Interpret the result in a planning record

The percent change calculator divides the difference between later and earlier values by the earlier value. Use it for two quantities defined in the same way. If the earlier value is zero, a standard percentage change is undefined; show the absolute change and explain the baseline instead of inventing a finite growth percentage.

Save the input values, units and result together. Change one uncertain input at a time so you can see which assumption moves the answer. A displayed decimal is arithmetic precision, rather than evidence that the measurements or rates are equally precise.

More tools

Read the How to Compare US Counties Without Misreading the Data guide →