Percentage Calculator
Use this free online Percentage Calculator to handle the three most common percentage problems in seconds: what is X% of Y, what percent is X of Y, and the percentage change from one number to another. It is useful for students, shoppers comparing discounts, sales staff working out commissions, accountants checking margins, and anyone who needs a fast, reliable answer without reaching for a spreadsheet. Each panel works independently, so you can calculate a tip, mark up a price, or compare last month's sales against this month's without switching screens. Results appear instantly in your browser, no sign-up required.
How to Use
Choose the calculation type from the dropdown, enter your values, and click Calculate. This tool supports three common percentage operations: finding a percentage of a number, finding what percentage one number is of another, and calculating percentage change between two values.
This calculator provides general estimates only. Results may vary depending on your personal circumstances, current tax rules, fees, deductions, interest rates, and other factors. It should not be treated as financial, tax, legal, or professional advice.
How to Use This Percentage Calculator
Working out a percentage is straightforward — pick the panel that matches your question and fill in the two known values.
- Decide which question you are asking — a percentage of a number, what percent X is of Y, or the percentage change between two values.
- Type the two known numbers into the matching panel.
- The answer updates instantly below the inputs — no button to press.
- Read the result, including a brief breakdown of the calculation used.
- Adjust either input to recalculate; the value rounds to two decimal places by default.
Example Calculation
If you scored 38 out of 50 in a test, the calculation is (38 ÷ 50) × 100 = 76%. Your test score is 76%. If a $250 jacket is reduced by 20%, the discount is $250 × 0.20 = $50, leaving a final price of $200. And if last month's revenue was $4,000 and this month's is $5,200, the percentage change is ((5,200 − 4,000) ÷ 4,000) × 100 = 30% increase.
How This Percentage Calculator Works
A percentage is just a fraction expressed out of 100. Behind the scenes the calculator uses three standard formulas. To find a percentage of a number it multiplies the number by the percentage and divides by 100, so 15% of 200 becomes (15 × 200) ÷ 100 = 30. To find what percent one number is of another it divides the part by the whole and multiplies by 100, so 30 out of 200 is (30 ÷ 200) × 100 = 15%. For percentage change between two values it subtracts the old value from the new value, divides by the absolute old value, and multiplies by 100, so growing from 50 to 65 is ((65 − 50) ÷ 50) × 100 = 30% increase. The result is rounded to two decimal places for readability, and a negative percentage change is shown as a decrease. Because the maths runs in your browser there is no upload, no waiting, and no limit on how many calculations you can do — useful when you are checking a long invoice, comparing several discounts, or building a budget.
Last updated: May 2026. This calculator provides estimates only and should not be treated as financial, tax, or legal advice.
Frequently Asked Questions
How do I calculate the percentage of a number?
Multiply the number by the percentage and divide by 100. For example, 20% of 150 = (150 × 20) ÷ 100 = 30. The calculator does this automatically when you select "What is X% of Y?"
What is the formula for percentage change?
Percentage change = ((new value − old value) / old value) × 100. A positive result is an increase, a negative result is a decrease.
Can I use decimals or negative numbers?
Yes. The tool handles fractional inputs (like 12.5%) and negative original values, returning a result with up to six decimal places.
What's the difference between percentage points and percent change?
A percentage point is the absolute difference between two percentages. If a rate moves from 5% to 7%, that's 2 percentage points but a 40% relative increase. Use the percentage-change mode for the second.
Why does the percentage calculator say "Total cannot be zero"?
Dividing by zero is undefined. If you're calculating "X is what percent of Y", Y must be non-zero. Try a different total value.
This calculator provides general estimates only. Results may vary depending on your personal circumstances, current tax rules, fees, deductions, interest rates, and other factors. It should not be treated as financial, tax, legal, or professional advice.