Percentage Calculator

How to Use the Percentage Calculator

This free percentage calculator handles three of the most common percentage problems you encounter in everyday life. Select a calculation mode from the dropdown, enter your two values, and the result appears instantly. In "What is X% of Y?" mode, enter the percentage as X and the base number as Y to find the resulting value. In "X is what % of Y?" mode, enter the part as X and the whole as Y to discover the percentage. In "% change from X to Y" mode, enter the original value as X and the new value as Y to see how much something has increased or decreased in percentage terms.

Percentages show up everywhere, from calculating sales tax and tip amounts to understanding investment returns and exam scores. Rather than reaching for a physical calculator or trying to do the math in your head, this tool gives you an accurate answer in real time as you type. It handles decimals, large numbers, and negative values without any trouble.

Understanding Percentage Formulas

Every percentage calculation boils down to a simple relationship between three quantities: the part, the whole, and the percentage. The core formula is Part = (Percentage / 100) x Whole. Rearranging this formula gives you the other two modes. To find the percentage: Percentage = (Part / Whole) x 100. To find the whole when you know the part and percentage: Whole = Part / (Percentage / 100).

Percentage Change Formula

Percentage change measures how much a value has grown or shrunk relative to its original size. The formula is % Change = ((New Value - Old Value) / Old Value) x 100. A positive result means an increase, while a negative result means a decrease. This is widely used in finance to track stock performance, in economics to measure inflation, and in science to compare experimental results. Note that the old value cannot be zero, since division by zero is undefined.

Practical Applications of Percentages

Percentages are essential in personal finance for calculating interest rates, discounts, and taxes. Retailers use them to express discounts ("30% off"), banks use them for interest rates, and governments use them for tax brackets. In academics, test scores are often expressed as percentages to standardize performance across different exams. Scientists use percentage error to quantify how close a measurement is to the true value. Understanding percentages empowers you to make better decisions about money, health metrics, and data analysis.

Frequently Asked Questions

How do I calculate what percent one number is of another?

Divide the part by the whole, then multiply by 100. For example, to find what percent 25 is of 200: (25 / 200) x 100 = 12.5%. This formula works for any two numbers where you need to express the first as a percentage of the second.

How do I find a percentage of a number?

Multiply the number by the percentage and divide by 100. For example, 15% of 200 is (200 x 15) / 100 = 30. Alternatively, convert the percentage to a decimal (15% = 0.15) and multiply: 200 x 0.15 = 30.

How do I calculate percentage change?

Subtract the old value from the new value, divide the result by the old value, and multiply by 100. The formula is: ((New - Old) / Old) x 100. A positive result indicates an increase, and a negative result indicates a decrease.

What is the difference between percentage and percentile?

A percentage is a fraction of 100 representing a part of a whole. A percentile indicates a value below which a certain percent of observations fall. For example, scoring in the 90th percentile means you scored better than 90% of all test takers.

Can a percentage be greater than 100%?

Yes. A percentage greater than 100% means the part exceeds the whole. For example, if a stock price rises from $50 to $120, the percentage change is 140%, meaning the new value is 2.4 times the original.