Online Percentage Calculator

How to Calculate Percentages

Percentages are a fundamental part of mathematics and are used everywhere from calculating discounts at a store to analyzing statistical data. Here are the formulas behind each of the calculators above.

1. How to find a percentage of a number? (What is X% of Y?)

This is the most common percentage calculation. To find the percentage of a number, you convert the percentage to a decimal and multiply it by the total number.

(X / 100) * Y = Result

Example: To find 20% of 300, the calculation is (20 / 100) * 300 = 60.

2. How to find what percent one number is of another? (X is what % of Y?)

This calculation is used when you want to express one number as a percentage of another. You divide the "part" (X) by the "whole" (Y) and then multiply by 100.

(X / Y) * 100 = Result %

Example: To find what percent 50 is of 200, the calculation is (50 / 200) * 100 = 25%.

3. How to calculate percentage change?

This is used to determine the degree of change over time, often to measure growth or decline. The formula finds the difference between two values, divides it by the original value, and multiplies by 100.

((New Value - Old Value) / |Old Value|) * 100 = % Change

Example: If a price increases from $150 to $180, the percentage increase is ((180 - 150) / 150) * 100 = 20% increase. If it decreases from $150 to $120, it is ((120 - 150) / 150) * 100 = -20%, or a 20% decrease.