Use the calculator below for any percentage question: what a percentage of a number is, what percent one number is of another, or how much something increased or decreased. Pick the tab that matches your question, enter the numbers, and get the answer instantly. No sign-up, no limits, and it works the same way every time.
How to Use This Percentage Calculator
There are three common percentage questions, and this tool covers all of them in one place.
- “What is X% of Y?” Use this when you know a percentage and a number, and want the result. For example, 20% of 150 is 30. This is the tab to use for discounts, tips, or commission.
- “X is what % of Y?” Use this when you have two numbers and want to know what percentage one is of the other. For example, 30 is 20% of 150. This is useful for test scores, budgets, or comparing a part to a whole.
- “% increase or decrease” Use this when a value changed over time and you want to know the percentage change. Enter the starting value and the new value, and the tool tells you whether it went up or down, and by how much.
Pick the tab that matches your situation, type in your two numbers, and click Calculate. The math happens instantly in your browser, nothing is sent to a server.
The Percentage Formulas Behind Each Calculation
If you want to understand the math rather than just get the answer, here is what each tab is actually calculating.
What is X% of Y? The formula is (X ÷ 100) × Y. So for 20% of 150, you divide 20 by 100 to get 0.2, then multiply by 150 to get 30.
X is what % of Y? The formula is (X ÷ Y) × 100. For 30 is what percent of 150, you divide 30 by 150 to get 0.2, then multiply by 100 to get 20%.
Percentage increase or decrease. The formula is ((New − Old) ÷ Old) × 100. Going from 80 to 100, you get (20 ÷ 80) × 100, which is 25%. A negative result means the value decreased.
Common Places You’ll Use Percentages
Percentage math shows up constantly in everyday decisions, even when it does not look like a math problem at first.
- Shopping discounts. A 30% off sale on a $60 item means the discount is 30% of 60, which is $18 off, so the item costs $42.
- Tips. A 15% tip on a $45 bill is 15% of 45, or $6.75.
- Grade or test scores. If you got 42 out of 50 questions right, that is 42 is what percent of 50, which comes out to 84%.
- Salary raises. If your salary went from $50,000 to $54,000, that is a percentage increase of 8%.
- Price changes. If a stock or a rent price dropped from $1,200 to $1,100, that is a percentage decrease of about 8.3%.
Frequently Asked Questions
Is this percentage calculator free to use?
Yes, completely. There is no limit on how many times you can use it, and no account is needed.
Does it work for negative numbers?
Yes. If you enter a negative number in the increase or decrease tab, the calculator will still return an accurate result.
Why is my percentage change showing as negative?
A negative result in the increase or decrease tab means the value went down rather than up. For example, going from 100 to 80 shows a decrease of 20%.
Can I use decimals?
Yes, the calculator accepts decimal numbers in every field, so you can work with prices, scores, or measurements that are not whole numbers.