Percentage Calculator

Percentages are everywhere -- from sales tax and restaurant tips to investment returns and exam scores. Despite being one of the most commonly used mathematical concepts, percentage calculations can trip people up, especially when dealing with percentage changes versus percentage differences. This free percentage calculator handles all four major types of percentage problems in one place.

The calculator runs entirely in your browser. As you type numbers, the result updates instantly with no page reloads or server requests. This makes it ideal for quick mental-math checks, homework help, or business calculations where you need answers fast.

The four calculation modes cover every common scenario. "What is X% of Y?" handles the classic percentage-of-a-number problem: discounts, tips, tax amounts, and commission calculations. "Y is what percent of Z?" solves the reverse question, useful when you know the part and the whole but need the rate. "Percentage change from X to Y" calculates how much a value increased or decreased relative to the original -- the go-to formula for year-over-year growth, stock gains, or weight-loss progress. Finally, "Percentage difference between X and Y" gives you the symmetric comparison between two values, using their average as the reference point rather than treating either as the "original."

Understanding the distinction between percentage change and percentage difference matters. Change is directional (going from 50 to 75 is +50%, but from 75 to 50 is -33.3%). Difference is symmetric (the difference between 50 and 75 is always 40%, regardless of order). Our tool makes the math trivial so you can focus on interpreting the result.

All four modes are available as tabs above the input fields. Switch between them freely -- the calculator remembers your inputs. Results are shown with up to two decimal places for precision, and the formula used is displayed alongside the answer so you can verify the math or learn the approach.

All calculations are performed client-side using standard mathematical formulas. No data is sent to any server. The formulas are: X% of Y = (X / 100) * Y; Y is what % of Z = (Y / Z) * 100; % change = ((New - Old) / Old) * 100; % difference = |X - Y| / ((X + Y) / 2) * 100.