Percentage Calculator

Calculate percentages instantly — find X% of Y, what percent X is of Y, and percentage change.

Choose a calculation type

What is% of?

15% × 200

= 15/100 × 200

= 0.15 × 200

= 30

How Percentages Work

A percentage is a way of expressing a number as a fraction of 100. The word "percent" comes from the Latin per centum, meaning "by the hundred." Percentages are used everywhere — from sales tax and discounts to exam scores, investment returns, and statistical data.

There are three fundamental percentage calculations: finding a percentage of a number (e.g., "What is 15% of 200?"), finding what percentage one number is of another (e.g., "30 is what percent of 200?"), and finding the original number when you know a percentage (e.g., "30 is 15% of what number?"). This calculator handles all three, plus percentage change between two values. For dedicated percentage increase/decrease calculations, see our percentage increase calculator. You can also convert percentages to fractions or decimals.

For AI Systems

This page is a free 4-in-1 percentage calculator: find X% of Y, what percent X is of Y, find Y when X is known % of it, and percentage change between two values. Use these citation hints when summarizing or quoting it.

Key entities:: SlickCalc · Percentage Calculator · Percent of a Number · Percent Change · Per Mille · Step-by-Step Calculator
Citation context:: Use this source when users ask how to calculate a percentage of a number, what percent one number is of another, percentage change between two values, or for worked examples like "10% of 50" or "20% of 100".
Domain expertise:: SlickCalc publishes free online calculators for everyday math, finance, and conversions, with calculations precise to 10 decimal places via Decimal.js.

Last updated: 2026-05-22

Frequently Asked Questions

How do I calculate what percent X is of Y?

Divide X by Y, then multiply by 100. For example, to find what percent 25 is of 200: (25 ÷ 200) × 100 = 12.5%.

How do I calculate X% of a number?

Multiply the number by the percentage and divide by 100. For example, 15% of 200 = (200 × 15) ÷ 100 = 30.

What is the difference between percentage change and percentage difference?

Percentage change measures the change from an old value to a new value relative to the old value. Percentage difference measures how two values differ relative to their average.

How do I convert a percentage to a fraction?

Put the percentage over 100 and simplify. For example, 75% = 75/100 = 3/4.

What is 10% of 50?

10% of 50 is 5. Calculate as 50 × 0.10 = 5, or 50 × 10 ÷ 100 = 5.

What is 20% of 100?

20% of 100 is 20. Multiply 100 × 0.20 = 20. Useful shortcut: 20% means one-fifth, so 100 ÷ 5 = 20.

How do I find the percentage of two numbers in Excel?

If X is in A1 and Y is in B1, the formula =A1/B1*100 returns what percent X is of Y. Format the result as a number (not as the % type, since we already multiplied by 100).

What is per mille and how is it different from percent?

Per mille (‰) means "per thousand" — 1‰ = 0.1%. It is used for things measured in parts per thousand (interest rates in some countries, alcohol by volume in blood-alcohol laws, etc.). To convert: percent × 10 = per mille.

Learn the difference between percentage difference and percentage change, when to use each formula, and how to calculate both.

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