How is the rate of change calculated?

The rate of change is (this period's value − base value) ÷ base value × 100 (%). A positive result means an increase and a negative result means a decrease.

What is the difference between the rate of change and the ratio to the prior period?

The prior-period ratio is this value ÷ base value × 100, where 100% means unchanged and 120% means 1.2 times as large. The rate of change is simply that ratio minus 100, so a 120% ratio equals a +20% rate of change.

Can I use it when the base value is zero, or for periods other than years?

If the base value is zero the rate and ratio cannot be computed because you cannot divide by zero. Otherwise you can compare any two points, such as last month vs this month or target vs actual, not just year over year.

Percent Change & Year-over-Year Calculator

Enter a starting (old) value and an ending (new) value to instantly get the percent change, the year-over-year ratio, and the absolute difference. Great for sales, prices, population, and traffic growth.

Last updated: July 7, 2026

Input

Old value (base)

New value (compare)

Result

Percent change

+20%

Increased

Difference

+20

Year-over-year ratio

120%

How it works

Percent change (rate of change) = (new value − old value) ÷ old value × 100 (%). A positive result means an increase; a negative result means a decrease.
Year-over-year ratio = new value ÷ old value × 100 (%). 100% means unchanged, and 120% means 1.2× the old value. Percent change = ratio − 100.
The difference is 'new value − old value', the absolute amount of change. A plus sign is shown when the new value is larger.
When the old (base) value is 0, the percent change and ratio cannot be computed because you would divide by zero (no result is shown).
It is not limited to last year vs. this year — use it for any two points in time (last month vs. this month, target vs. actual). The percent change and ratio are rounded to two decimal places as a guide.

Frequently asked questions

How is the rate of change calculated?: The rate of change is (this period's value − base value) ÷ base value × 100 (%). A positive result means an increase and a negative result means a decrease.
What is the difference between the rate of change and the ratio to the prior period?: The prior-period ratio is this value ÷ base value × 100, where 100% means unchanged and 120% means 1.2 times as large. The rate of change is simply that ratio minus 100, so a 120% ratio equals a +20% rate of change.
Can I use it when the base value is zero, or for periods other than years?: If the base value is zero the rate and ratio cannot be computed because you cannot divide by zero. Otherwise you can compare any two points, such as last month vs this month or target vs actual, not just year over year.

Reviews

Tell us what you think of this calculator.

Write a review

Report a bugFound an incorrect result or a problem? Turn this on to report it.

Nickname (optional)

Comment (optional)