Percentage Calculator — Percent Of and Change

How to use Percentage Calculator — Percent Of and Change

Three simple steps, with your content kept on your device.

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Fast, focused, and made to be clear on every screen.

What is a percentage?

A percentage is a fraction expressed out of 100. The word comes from per cent, meaning per hundred, so 25 percent means 25 out of every 100 parts. Percentages are the standard way to describe proportions in finance, shopping, statistics, and everyday life.

Because percentages always use the same base of 100, they make different-sized quantities comparable: a 10 percent discount on a 20 dollar item and a 10 percent discount on a 200 dollar item represent the same proportional saving, even though the amounts differ.

How to calculate a percentage of a number

To find a percentage of a number, multiply the number by the percentage and divide by 100. For example, 25 percent of 200 is 200 times 25 divided by 100, which equals 50.

The reverse question — what percentage one number is of another — is just as common: divide the part by the whole and multiply by 100. If 30 of 150 students passed, that is 30 divided by 150 times 100, or 20 percent.

Percentage increase and decrease

A percentage increase describes how much a value grew relative to its starting point. A price that rises from 80 to 100 has increased by 20, which is 25 percent of the original 80.

A percentage decrease works the same way in reverse: a price that falls from 100 to 80 has dropped by 20 percent. This calculator handles both directions, so you can apply a discount, add a markup, or measure a change.

Percentage difference explained

Percentage difference compares two values using their average as the reference point, so neither value is treated as the original. This makes it useful for symmetric comparisons, such as two measurements of the same quantity.

It differs from percentage change, which always measures relative to the starting value. Choosing the right one matters: change is directional, while difference is not.

Common uses for a percentage calculator

Shoppers use percentages to work out discounts and sales tax. Students use them to convert test scores into percentages and grade boundaries. Analysts use them to measure growth, market share, and margins.

This tool covers the three most frequent calculations — percentage of a number, percentage change, and percentage difference — so the right formula is always one click away.

Why calculations happen locally

Every calculation runs in your browser without a network request. The numbers you enter never leave your device, so the tool is safe for pricing, salaries, and financial data.

There is no account and nothing is stored. Open the page, enter your values, and the result appears instantly.

Percentages in shopping and discounts

Sales and discounts are the most common place people meet percentages. To work out the final price, take the original price, calculate the discount percentage of it, and subtract the result. A 30 percent discount on a 90 dollar item saves 27 dollars, leaving a price of 63.

You can also calculate percentage in reverse: if an item was 60 dollars and now costs 45, the discount is 15 dollars, which is 25 percent of the original price. Both directions are built into this tool.

Percentages in statistics and data

Percentages are the standard way to report parts of a whole in statistics: what share of a survey agreed, what fraction of a budget is spent, or how much a metric grew between two periods.

The percentage change mode is the right tool for growth rates and comparisons over time, while the percentage difference mode suits symmetric comparisons where neither value is the reference.

Percentages in finance and money

Interest rates, tax, tips, and margins are all expressed as percentages. A savings account earning 4 percent a year grows a 1,000 dollar balance by 40 dollars, and a 15 percent tip on an 80 dollar meal is 12 dollars.

Because the math is identical everywhere, one tool covers all of them: enter the base number and the percentage, and the calculator does the rest without rounding errors or mental arithmetic.

Frequently asked questions