Free Percentage Calculator
Five calculators in one — solve any percentage problem instantly.
What is X% of Y?
X is what % of Y?
Percentage change from X to Y
Part is what % of whole?
X is Y% of what?
Running Total
What is a percentage calculator?
A percentage calculator is a free tool that solves any type of percentage problem: finding what percentage one number is of another, calculating a percentage of a value, or computing the percentage change between two numbers. Instead of remembering three different formulas, you pick the calculation type and enter the numbers you know.
Percents are one of those things everyone runs into but nobody wants to do long division for. Fifteen percent of what number? What percentage did I get on that test? By how much did my rent go up? This calculator covers the five most common scenarios in separate tabs — you pick the one that matches your question, plug in the numbers, and done. Also keeps a running history so you can go back and reference earlier calculations.
Most percentage calculators give you one mode and make you figure out which formula to use on your own. This one has five tabs that cover practically every situation: what is X% of Y, X is what percent of Y, percentage change (increase or decrease), part out of whole, and the reverse "X is Y% of what" for when you know the result but not the original number. Each mode shows the formula it used so you can double-check the math.
How the percentage calculator works
Pick the tab that matches your question. In the "What is X% of Y?" tab, the calculator multiplies your number by the percentage as a decimal — like 0.15 × 200 = 30 for 15% of 200. In the "X is what % of Y?" tab, it divides the part by the whole and multiplies by 100 — so 30 out of 200 is 15%. The "change" tab uses ((new - old) ÷ old) × 100, which handles both increases (positive result) and decreases (negative result).
Everything updates as you type — there's no Calculate button to press. Positive percentage changes show in green with an up arrow, negative ones in red with a down arrow. Your active tab and last numbers are saved in your browser, so if you close the page and come back, they're still there. That running history at the bottom keeps track of every calculation you've done in the session, which is handy when you're comparing numbers side by side.
Common percentage calculator uses
The percentage calculator handles a wide range of everyday scenarios. Use it to calculate sales tax by finding X% of a price. Determine your grade by computing your score as a percentage of the total. Find the percentage markup on a product by calculating the percentage change from cost to selling price. Check whether a raise is fair by computing the percentage increase in salary. Compare two data points across time — revenue, weight, speed, or any metric — using percentage change. Restaurants use it to determine tip percentages, retailers use it to calculate discounts, and fitness enthusiasts use it to track body fat or weight loss as a percentage of starting values.
For financial calculations specifically, percentage change is particularly useful: a stock moving from $42 to $56 represents a 33.3% gain, while a drop from $56 to $42 is only a 25% loss — the asymmetry of percentage gains and losses is why the direction (from to) matters in the formula. Real estate agents calculate commission percentages, investors track portfolio returns as percentage change, and shoppers compare unit pricing using percentage differences across package sizes. The percentage calculator works for any numeric value — positive, negative, zero, or decimal — with results up to four decimal places for precise financial work.
Percentage increase vs percentage points
A common source of confusion: if an interest rate rises from 2% to 3%, it has increased by 1 percentage point but by 50% in relative terms. Percentage points measure the arithmetic difference between two percentages; percentage change measures how large that difference is relative to the starting value. Our percentage change calculator uses the relative (percentage change) formula, which is standard in finance, statistics, and business reporting. Understanding this distinction is important when reading news about interest rates, inflation, unemployment, and other economic indicators — journalists often use both measures, and confusing them can lead to serious misinterpretation of the data.
When a central bank raises rates from 1% to 1.25%, that is a 25-basis-point increase (0.25 percentage points) but a 25% increase in the rate itself. The "percentage change" mode of our calculator correctly computes the relative change, which is the figure most commonly cited in financial news and investment analysis.
How to use this calculator
- Choose a calculation type — Pick one of five modes: find a percentage of a number, find what percentage one number is of another, calculate the percentage change between two values, determine a part as a percentage of a whole, or find the whole when you know a part and percentage.
- Enter your numbers — Type the values into the input fields. Results update automatically as you type — no Calculate button needed.
- Read your answer — The result appears instantly below the inputs, including the full formula so you can see exactly how the answer was reached.
Frequently asked questions
What is 15 percent of 200?
15% of 200 is 30. Multiply 200 × 0.15 = 30. A quick mental method: find 10% first (move the decimal left one place: 20), then find 5% (half of 10%: 10), and add them: 20 + 10 = 30. The calculator above handles any percentage instantly — enter 15 in the percentage field and 200 as the number.
How do I calculate percentage increase between two numbers?
Percentage increase = ((New Value - Old Value) / Old Value) × 100. If a price rises from $80 to $100: (($100 - $80) / $80) × 100 = 25% increase. If the new value is lower, the result is negative — that's a percentage decrease. Use the 'percentage change' section of the calculator for this type of problem.
What percent of 80 is 20?
20 is 25% of 80. Divide the part by the whole and multiply by 100: (20 ÷ 80) × 100 = 25%. This answers 'X is what percent of Y?' questions. Enter 20 as the part and 80 as the whole in the 'what percent' section above to verify and solve similar problems.
How do I calculate a percentage decrease?
Percentage decrease = ((Original Value - New Value) / Original Value) × 100. If enrollment drops from 500 to 425 students: ((500 - 425) / 500) × 100 = 15% decrease. Always divide by the original (starting) value, not the new value. Dividing by the new value gives a different — and incorrect — result.
How do I add a percentage to a number?
To add a percentage to a number, multiply the number by (1 + percentage/100). Adding 8% tax to a $50 item: $50 × 1.08 = $54. Or calculate the percentage amount first ($50 × 0.08 = $4) and add it: $50 + $4 = $54. Both methods give the same result. The calculator's 'add percentage' field does this automatically.
How do I find the original price before a percentage increase?
Divide the final price by (1 + the percentage rate). If a price is $108 after a 8% increase, the original was $108 ÷ 1.08 = $100. A common mistake is subtracting 8% from $108 ($99.36) — that gives the wrong answer because the percentage was applied to the original amount, not the final.
How do I calculate percent off on a price?
Multiply the original price by (1 - discount percentage/100). A $80 jacket at 25% off: $80 × 0.75 = $60. You can also find the discount amount first ($80 × 0.25 = $20) and subtract it: $80 - $20 = $60. The 'Find %' tab works for percent off too — enter the discount percentage and the original price, then subtract the result from the price.