Percentage Calculator
Calculate a percentage of a number, what percent one value is of another, or the percentage change between two numbers.
What This Percentage Calculator Does
Percentages come up everywhere — discounts, grades, statistics, and everyday comparisons. This tool covers the three most common percentage questions in one place: finding a percentage of a number, working out what percentage one number is of another, and calculating the percentage change between two values.
How Each Calculation Works
% of a Number: multiplies the number by the percentage divided by 100. For example, 20% of 500 is (20 ÷ 100) × 500 = 100.
What Percent: divides the first number by the second and multiplies by 100, telling you what share one value represents of another.
% Change: compares a starting value to an ending value and reports whether it increased or decreased, and by what percentage.
Frequently Asked Questions
How do I calculate 20% of 500?
Enter 20 in the percentage field and 500 in the "of number" field on the first tab. The calculator will show that 20% of 500 is 100.
What's the difference between the three tabs?
Each tab answers a different question: a share of a number, what percentage one number is of another, and how much a value has increased or decreased.
Can percentages be negative?
A percentage change can be negative, which the calculator reports as a decrease rather than a negative increase.
How to check this result
Start by deciding which number is the whole and which number is the part. This prevents the most common percentage mistake.
Method and assumptions
A percentage is a part divided by a whole, multiplied by 100. Percentage change compares the difference with the original value.
Before making a decision
For a price change, always confirm whether the percentage is a discount, an increase, or a tax.
Choosing the correct percentage base
Method and inputs
For a share, divide the part by the whole and multiply by 100. For percentage change, subtract the old value from the new value, divide by the old value, then multiply by 100. A zero whole or starting value makes those divisions undefined.
Worked example
A price rises from 80 to 100: (100 − 80) ÷ 80 × 100 = 25%. Reversing the change gives (80 − 100) ÷ 100 × 100 = −20%. The different answers come from different starting values.
Limits and common mistakes
A 20% fall followed by a 20% rise leaves 96% of the starting amount. Percentage points are different: moving from 10% to 15% is five percentage points, but a 50% relative increase.
Can I compare percentages with different totals?
Only after checking the denominators. Ten successes out of 20 and ten out of 100 have the same count but different shares.
Content updated: 2026-10-03.
Reference for checking the method
Percent means per hundred; the whole is the denominator.
This reference explains the concept; its publisher has not verified or endorsed this calculator.