Percentage Calculator
Percent of a number and percentage change.
A percentage calculator is a tool that expresses one number as a fraction of another and converts that fraction into a value out of 100. The percent symbol (%) was standardised in the 20th century and now appears across finance, science, retail and everyday life. This calculator handles the two percentage questions people ask most often, without any manual arithmetic.
How This Percentage Calculator Works
This calculator works two ways at once. Enter a percentage and a number, and it returns the part. It follows PEMDAS, the standard order of operations, so multiplication and division always run in the correct order. Enter an old value and a new value, and it returns the percentage change between them, updating both results as you type.
What You Can Calculate
- What a given percentage of a number equals
- The percentage change between an old value and a new value
The Percentage Formula
Worked example
If 15 students in a class of 60 passed an exam, 15 is the numerator and 60 is the denominator. Divide the numerator by the denominator to get 0.25. Multiply 0.25 by 100 and the pass rate is 25 percent. The calculator runs this in under a second and removes any room for arithmetic error.
Percentage Change and Percentage Difference
Say a product cost 80 last month and costs 100 today. The change is 20, and 20 divided by the original 80 is 0.25. Multiply by 100 and the percentage increase is 25 percent.
The same formula works in reverse for a price that falls. A drop from 100 to 80 is a 20 percent decrease. Businesses, economists and students use this method to track price movements, population shifts and exam score trends.
Percentage difference is a related but separate idea. It compares two values without treating either one as the start, and divides the gap by their average. It answers “how different are these two figures?” rather than “how much has one changed?” and suits lab measurements and store price checks.
Where Percentages Appear in Daily Life
Percentages appear wherever a proportion needs to be shown clearly. Shops use them for discounts and governments use them for tax rates on income and purchases. Banks quote interest on savings and loans in them, schools grade exams with them and health apps track body fat with them.
- Retail discounts → finding the sale price after a percentage off
- Tax calculations → applying the tax rate to a taxable income or purchase amount
- Finance → calculating interest as a percentage of principal
- Health → expressing body fat or nutrition as a fraction of total intake
- Education → converting raw scores into percentage marks
Frequently asked questions
What is a percentage calculator used for?
It converts a part and a whole into a percentage, and finds the percentage change between two values.
How do I calculate what percentage one number is of another?
Divide the first number by the second and multiply by 100 to get the percentage.
What is the difference between percentage change and percentage difference?
Percentage change measures movement from a starting value. Percentage difference compares two values without treating either one as the starting point.
Can this calculator find a percentage increase or decrease?
Yes, enter the old and new values and it returns the increase or decrease as a percentage.
Is this percentage calculator free?
Yes, it runs in any browser with no sign up required.
Related calculators
Other tools people use alongside the percentage calculator.