Percentage Calculator
Work out X% of Y, what percentage X is of Y, the percentage change between two values, and a number increased or decreased by a percentage.
What is X% of Y?
X is what % of Y?
Percentage Change
Increase/Decrease by %
Use a negative percentage (e.g. -20) to decrease.
About the Percentage Calculator
Four small calculators cover the percentage questions that come up most often, each with its own inputs and Calculate button. What is X% of Y? multiplies Y by X ÷ 100, so 18% of 2,500 is 450. X is what % of Y? divides X by Y and multiplies by 100, so 45 out of 60 is 75%. Percentage Change compares a starting value with a new one: from 80 to 100 is +25%. Increase/Decrease by % applies a percentage to a number: 1,200 increased by 15% is 1,380, and entering −15 instead gives 1,020. Results are rounded to two decimal places.
Percentage change is always measured against the starting value, which is why it isn't symmetrical. Going from 80 to 100 is +25%, but going back from 100 to 80 is −20%, because the same difference of 20 is divided by a different starting number. It is also why a 20% discount followed by a 20% price rise doesn't bring you back where you started: 1,000 becomes 800, then 960.
Typical uses include working out exam marks as a percentage, checking a discount or a salary increase, and comparing sales or prices between two periods. For tax on a price, the GST Calculator adds or removes GST directly, and the Tip Calculator handles tips and bill splitting.
How to use the Percentage Calculator
- 1
Pick the right card
Choose What is X% of Y?, X is what % of Y?, Percentage Change, or Increase/Decrease by %.
- 2
Enter the two numbers
Fill in both boxes on that card. For a decrease, type a negative percentage such as -20 in the Increase/Decrease card.
- 3
Press Calculate
The answer appears below the button. If you change a number, press Calculate again to update it.
What it can do
Four common calculations
Percent of a number, one number as a percentage of another, percentage change, and increase or decrease by a percentage.
Signed percentage change
Increases are shown with a + sign and decreases with a − sign.
Divide-by-zero check
If Y or the starting value is 0, the card explains that the answer is not defined instead of showing a meaningless number.
Decimals and negative numbers
All boxes accept decimals and negative values.
Limitations
- Results are rounded to two decimal places, so very small results may show as 0.00.
- Results don't update automatically; press Calculate after changing an input.
- A change between two percentages, such as 10% to 12%, is shown as a relative change (+20%), not as a change in percentage points (+2).
- It doesn't do repeated or compound percentages, such as growth over several years.
Privacy
The numbers you enter are calculated in your browser and are not sent to FlexyPdf's servers.
Frequently asked questions
How do I work out a percentage of a number?
Multiply the number by the percentage and divide by 100. In the What is X% of Y? card, enter the percentage as X and the number as Y: 12.5% of 640 is 80.
How do I calculate my marks as a percentage?
Use X is what % of Y?. Enter the marks you scored as X and the maximum marks as Y. For 432 out of 500, the result is 86.4%.
How do I take a discount off a price?
Use Increase/Decrease by % with a negative percentage. A price of 2,499 with 30% off is 2,499 by −30, which gives 1,749.30.
Why is a percentage increase not the same as the matching decrease?
Because each is divided by its own starting value. Rising from 50 to 75 is +50%, but falling from 75 to 50 is about −33.33%. The difference is the same 25, but the base changes.
What happens with a starting value of zero or below zero?
A starting value of 0 has no percentage change, so the card says the result is not defined. For negative starting values, the change is divided by the size of the starting value, so going from −50 to −25 shows +50%, an increase.
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