Percentage Calculator
Three quick percentage tools in one. Fill in any of the calculators below and the answer appears instantly.
What is X% of a number?
X is what percent of Y?
Percentage increase / decrease
About this percentage calculator
Percentages come up constantly — discounts, test scores, tips, statistics and more. This calculator bundles the three most common percentage questions into one page so you can get an answer in seconds, whichever type of calculation you need.
How to use it
- Pick the calculator that matches your question.
- Type your numbers into the boxes.
- The answer appears instantly as you type.
How it works (the formula)
- X% of Y = Y × (X ÷ 100)
- X is what % of Y = (X ÷ Y) × 100
- Percentage change = (New − Old) ÷ Old × 100
Worked example
20% of 150 = 150 × 0.20 = 30. And a change from 80 to 100 = (100 − 80) ÷ 80 × 100 = +25%.
Common uses
- Discounts and sale prices
- Tips and service charges
- Test scores and grades
- Profit, growth, and change rates
Tips & common mistakes
- A percentage increase followed by the same percentage decrease does not return the original number — each applies to a different base.
- Always divide the change by the original value, not the new one.
Frequently asked questions
How do I find a percentage of a number?
Multiply the number by the percentage and divide by 100. For example, 20% of 150 is 150 × 20 ÷ 100 = 30. The first calculator does this for you.
How do I calculate percentage increase?
Subtract the old value from the new value, divide by the old value, then multiply by 100. The third calculator handles increases and decreases automatically.
What is the difference between the three calculators?
The first finds a percentage of a number, the second finds what percent one number is of another, and the third finds the percentage change between two numbers.
Why isn't a 20% increase then a 20% decrease back to the start?
Each percentage applies to a different base. +20% of 100 is 120, but −20% of 120 is 96 — not 100. So equal percentage moves up and down do not cancel out.
How do I find the original price before a percentage was added?
Divide the final amount by (1 + percentage/100). For example, if a price is 120 after a 20% increase, the original was 120 ÷ 1.20 = 100.
Is it private?
Yes — all calculations happen in your browser.
Related tools
Try the Discount Calculator or Tip Calculator.