Percentage Calculator
Calculate percentages, increases, decreases and changes instantly.
What Are Percentages?
A percentage is a way of expressing a number as a fraction of 100. The word comes from the Latin "per centum," meaning "by the hundred." Percentages are one of the most widely used mathematical concepts in everyday life — from calculating tips and taxes to understanding interest rates, exam scores, discounts, and statistical data. Whether you're shopping, managing finances, or analyzing data, understanding percentages is essential.
How to Calculate Percentages
There are four fundamental percentage calculations. "What is X% of Y?" — multiply Y by X/100. For example, 15% of 200 = 200 × 0.15 = 30. "X is what % of Y?" — divide X by Y and multiply by 100. For example, 30 is what % of 200? → 30/200 × 100 = 15%. "Percentage change" — subtract old from new, divide by old, multiply by 100. "Add/subtract percentage" — calculate the percentage amount and add or subtract from the original.
Percentage Change in Business
Percentage change is critical in business for measuring growth, decline, and performance. Revenue growth of 25% year-over-year, stock price dropping 10%, profit margins increasing by 3 percentage points — these metrics drive business decisions. Understanding the difference between "percentage change" and "percentage points" is crucial: if a rate goes from 10% to 15%, that's a 5 percentage point increase but a 50% percentage change.
Percentages in Finance
In finance, percentages are everywhere. Interest rates on savings and loans, annual percentage rate (APR), return on investment (ROI), profit margins, tax rates, and inflation are all expressed as percentages. Understanding these calculations helps you compare financial products, evaluate investments, and make informed decisions about borrowing, saving, and spending. A 1% difference in mortgage rate can mean tens of thousands of dollars over a 30-year loan.
Common Percentage Mistakes
The most common mistake is assuming percentages are additive. A 50% increase followed by a 50% decrease does NOT return to the original — it results in 75% of the original. Similarly, a 20% discount followed by an additional 10% off isn't 30% off; it's 28% off the original price. Another common error is confusing "percentage of" with "percentage more than" — 25% more than 100 is 125, not 25.