Whether you're comparing this month's sales to last month's, tracking a raise in your paycheck, or figuring out how far a stock has moved, a percentage change calculator answers the same question every time: how big was the swing, expressed as a percent? Enter your starting and ending numbers and the tool instantly returns the percentage increase or percentage decrease between them. Below, you'll find the formula broken down step by step, worked examples with negative numbers, and the real-world math — from population growth rate to compound interest — that makes this kind of calculation one of the most useful things you can do with two numbers.
What Is a Percentage Change Calculator?
At its core, a percentage change calculator applies a single piece of mathematics: it takes two numbers and expresses the gap between them as a percent rather than a flat amount. This differs from simply subtracting one number from another, because percentage change accounts for scale — a $10 increase means far more to a $50 budget than to a $5,000 one. That's why the calculator is used across finance, business, economics, and statistics, and in science and mathematics classrooms, whenever people need to compare change relative to a starting point rather than as a raw number. The same relationship can be written as a decimal or a percent — the calculator just automates that ratio-to-percent conversion for you. Some sites call this a percent change calculator instead of a percentage change calculator; they're the same tool under two names.