Percentage Calculator
Calculate a percentage of a number, find what percent one value is of another, and measure percentage increase, decrease or difference.
What can this percentage calculator do?
- Find a percentage of any number.
- Calculate what percentage one value is of another.
- Measure percentage increase.
- Measure percentage decrease.
- Compare two values using percentage difference.
Common percentage examples
You can use this calculator for discounts, marks, profit margins, price changes, growth rates, salary increases, business performance and everyday math.
Frequently asked questions
How do I calculate 20% of 500?
Select “What is X% of Y?”, enter 20 and 500, then calculate. The result is 100.
How is percentage increase calculated?
Percentage increase compares the increase with the original value.
What is percentage difference?
Percentage difference compares two values using their average as the reference point.
How to interpret percentage results correctly
A percentage describes a part relative to a whole, but the same number can mean different things depending on the question. “20% of 500” asks for a portion, while “500 is what percent of 2,000?” asks for a ratio. Percentage increase or decrease compares a new value with the original starting value.
Percentage change uses the original value
For an increase or decrease, the original number is the denominator. Moving from 80 to 100 is a 25% increase because the change of 20 is compared with the original 80. Reversing the values does not produce the exact opposite percentage.
Useful checks
If a result seems surprising, estimate it mentally. Ten percent of a number is one tenth, so 20% is roughly twice that. A quick estimate helps catch swapped inputs or an incorrect interpretation before you use the result in a budget, discount, score or report.
Common percentage mistakes to avoid
A percentage change and a percentage-point change are not the same thing. If a rate moves from 20% to 25%, that is an increase of 5 percentage points, but the relative percentage increase is 25%.
Increase and decrease do not perfectly undo each other
If a value rises by 20% and then falls by 20%, it does not return to the starting value because the second calculation uses a different base. For example, 100 becomes 120 and then falls to 96.
Use the correct base value
When asking “what percent is A of B?”, B is the reference value. Swapping the numbers changes the question and the result. For price discounts, taxes and growth rates, identify the original or reference amount before calculating.
Rounding
The calculator can display decimal results, but financial documents, grades and reports may have their own rounding rules. Keep extra decimal places until the final step when precision matters.