The percent by which a number changes from an original value.
Percent of change tells us how much a value has increased or decreased, expressed as a percentage of the original value. It answers the question: by what percent did this number change?
The formula is:
Percent of Change = (Amount of Change ÷ Original Value) × 100
For example, if a jacket originally costs $40 and the price drops to $30, the amount of change is $10. Dividing by the original value: 10 ÷ 40 = 0.25, or 25%. The price decreased by 25%.
When a value goes up, we call it a percent of increase. When it goes down, we call it a percent of decrease. Both are calculated the same way — the direction of the change tells us which term to use.
Percent of change is one of the most practical math skills students learn. It shows up in sales and discounts, population growth, test score comparisons, and many other real-world situations.
When Do Students Learn About Percent of Change?
Students work toward percent of change through their study of percents, decimals, and proportional reasoning.
Grades 4–5 – Understanding Percents
Students learn what a percent is and how to convert between percents, decimals, and fractions. This is the foundation for all percent calculations.
Grades 6–8 – Calculating Percent of Change
Students are formally introduced to percent of change, applying it to real-world problems involving increases, decreases, discounts, and markups.
Grades 9+ – Percent of Change in Advanced Contexts
Students apply percent of change in more complex settings, including exponential growth and decay, statistics, and financial math.
