Everyday Tools
Percentage Calculator
Three common percentage questions from the same two numbers — pick which one to feature, all three are shown.
Calculation inputs
Enter X and Y, then choose which calculation to highlight.
Results
No result yet
Complete the fields and select Calculate to show results here.
About this calculator
A percentage calculator turns two numbers into the three questions people ask most: what a percent of a number is, what share one number is of another, and how much something has changed in percentage terms. Shoppers, students, and anyone checking a bill or a raise reach for it.
How the calculation works
- X% of Y = X ÷ 100 × Y
- X as a % of Y = X ÷ Y × 100
- Percentage change = (Y − X) ÷ |X| × 100
Notes and assumptions
Percentage change is measured from X to Y, so swapping the inputs gives a different answer.
How it works in plain English
Percentages are just fractions of 100, so every version of the question boils down to the same relationship between a part and a whole. Finding X% of Y multiplies Y by X divided by 100. Finding what percent X is of Y instead divides X by Y and multiplies by 100.
Percentage change compares two values across time or a transaction, such as a price before and after a sale. It takes the difference between the new and old figure, divides by the original figure, and expresses the result as a percentage. A positive result means growth, a negative one means a decrease.
Because all three calculations start from the same pair of numbers, entering X and Y once and choosing which question to highlight avoids re-typing the same figures three times. The other two results stay visible for comparison.
The formula
- X% of Y = (X / 100) x Y
- X is what % of Y = (X / Y) x 100
- Percentage change from X to Y = ((Y - X) / X) x 100
Worked example
A shirt costs $160 and is marked down by 25%. Using X = 25 and Y = 160, 25% of 160 is (25/100) x 160 = $40, so the discount is $40 and the sale price is $120. If instead you wanted to know what percent 40 is of 160, that's (40/160) x 100 = 25%. And if the price had moved from $160 last month to $120 this month, the percentage change is ((120-160)/160) x 100 = -25%, a 25% decrease. These three results are consistent because they all describe the same $40 gap between $120 and $160, just from different starting points. Recognizing that connection makes it easier to spot when a reported percentage change doesn't match the underlying dollar figures in a receipt or report.
Frequently asked questions
What is the difference between percent of and percent change?
Percent of finds a portion of a single number, like 20% of 50. Percent change compares two different numbers over time or across a transaction and tells you how much bigger or smaller the second one is, expressed as a percentage of the first.
Why is percentage change negative sometimes?
A negative percentage change means the second number is smaller than the first, so the value decreased. For example, going from 200 to 150 gives a change of -25%, showing a drop rather than growth.
Can percentages go above 100%?
Yes. If X is larger than Y, then X as a percent of Y exceeds 100%. This is normal and simply means the part is bigger than the whole you are comparing it to, such as 120 being 150% of 80.
How do I calculate a percentage increase back to the original number?
Divide the new number by (1 plus the percentage increase expressed as a decimal). For example, if 130 reflects a 30% increase, dividing 130 by 1.30 gives back the original value of 100. This works because the new number equals the original multiplied by that same factor, so dividing undoes the multiplication. The same logic in reverse, multiplying by (1 minus the percentage), recovers an original value from a number that reflects a percentage decrease instead of an increase.
Does rounding affect percentage results?
Yes, rounding intermediate steps can shift the final answer slightly, especially with repeating decimals. For most everyday purposes rounding to one or two decimal places is accurate enough, but financial calculations should carry more decimal precision.