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Percentage Calculator
Three calculations people actually need: what is X% of Y, what percent is X of Y, and the percent change from one number to another.
36
How to use it
- Choose the kind of percentage.
- Enter the two numbers.
- Read the result. A zero base is rejected for the two divisions.
- Switch modes without reloading the page.
Formulas
X% of Y = Y × X / 100. X is (X / Y) × 100 percent of Y. Change from A to B = (B − A) / A × 100.
Percent change uses the first number as the base. Swapping the numbers is a different question.
A price from 80 to 100
The change is (100 − 80) / 80 × 100 = 25%. The new price is 125% of the old price. A later drop from 100 to 80 is a 20% decrease, not a 25% decrease.
A percentage is a fraction of 100. Ten percent of 80 is 8, because 80 × 0.10 = 8. If 45 out of 60 answers are right, the score is 45 ÷ 60 × 100 = 75%. A price moving from 80 to 100 is a 25% increase, because the change is 20 and 20 ÷ 80 = 0.25. Going from 100 back to 80 is a 20% decrease. The direction matters, and the calculator uses the starting number as the base.
Questions
How do I calculate a percentage of a number?
Multiply the number by the percentage and divide by 100. Fifteen percent of 240 is 240 × 15 / 100 = 36.
How do I find what percent one number is of another?
Divide the part by the whole and multiply by 100. 18 out of 60 is 30%.
Why is a fall from 100 to 80 not 25%?
The base is 100, and you lost 20, which is 20%. The 25% figure is the rise from 80 to 100, where the base is 80.
Are the numbers uploaded?
No. The math runs locally.