EVERYDAY MATH
Percentage Calculator
Three quick ways to work with percentages. Pick a question and enter your numbers.
Percentage of a number
Find a tip, discount, or share of a total.
One number as a percentage
See how much one amount represents of another.
Percentage increase or decrease
Compare a starting value with a new value.
Accepts decimals and negative numbers. Results display up to 6 decimal places; very small values use scientific notation.
How to calculate percentages and percentage change
Use the first form to find a percentage of a number. Use the second form to find what percent one number is of another, and the third to compare a new value with a starting value. A positive change indicates an increase relative to a positive starting value; a negative change indicates a decrease.
Formula
Percentage = value × percent ÷ 100; ratio = part ÷ total × 100; change = (new − old) ÷ old × 100
Example
15% of 200 is 30, and 30 is 15% of 200. A change from 100 to 120 is a 20% increase, while a change from 100 to 80 is −20%.
Assumptions and limits
A percentage ratio is undefined when the total is zero. Percentage change is undefined when the starting value is zero. The signed formula is also available for negative starting values, where the usual increase/decrease interpretation needs care.