Percentage Calculator
Three percentage calculators in one: find X% of a number, work out what percent one number is of another, and measure percentage increase or decrease. Free, instant and fully private — everything is computed in your browser.
What is X% of Y?
X is what percent of Y?
Percentage increase / decrease
How to use the percentage calculator
- Pick the right calculator. Use the first box to find X% of a number, the second to see what percent one number is of another, and the third to measure the change between two values.
- Type your numbers. Results appear instantly as you type — decimals and negative values are fully supported.
- Copy the answer. Every result has its own 📋 Copy button, so you can paste the value straight into a document, spreadsheet or message.
About this tool
This free percentage calculator covers the three percentage questions people ask most often. "What is 20% of 150?" multiplies the number by the percentage divided by 100 (150 × 0.20 = 30). "30 is what percent of 150?" divides the part by the whole and multiplies by 100 (30 ÷ 150 × 100 = 20%). Percentage increase or decrease compares an old and a new value with the formula (new − old) ÷ |old| × 100, which is how discounts, price rises, pay raises and statistics changes are normally expressed.
It is handy for working out sale discounts and tips, VAT and sales tax, exam scores, interest, and month-over-month growth. All calculations run locally in your browser — nothing you type is uploaded, stored or logged, and the tool keeps working even when you go offline after the page has loaded.
Frequently asked questions
How do I calculate a percentage of a number?
Divide the percentage by 100 and multiply by the number. For example, 20% of 150 is (20 ÷ 100) × 150 = 30. The first calculator on this page does exactly that for any values, including decimals like 7.5%.
How is percentage increase or decrease calculated?
Take the difference between the new and old value, divide by the absolute old value, then multiply by 100: (new − old) ÷ |old| × 100. Going from 80 to 100 is a 25% increase; going from 100 to 80 is a 20% decrease. Note the two directions give different percentages because the starting base differs.
Why can't I compute a percentage change from zero?
Percentage change divides by the old value, and division by zero is undefined. Any change starting from 0 would be an "infinite" percentage, so the calculator shows an error instead of a misleading number.
What is the difference between percentage change and percentage points?
If an interest rate moves from 4% to 5%, it rose by 1 percentage point, but the relative percentage change is 25% (1 ÷ 4 × 100). Use percentage points when both values are already percentages and you want the simple difference.