Percentage calculator
Pick the question you are trying to answer, fill in two numbers and the calculator does the rest, showing the steps so you can learn the method.
How the percentage calculator works
A percentage is just a fraction out of 100, so most percentage questions come down to multiplying or dividing by 0.01 at the right moment. To find a percentage of an amount, turn the percentage into a decimal and multiply. To find what percentage one number is of another, divide the part by the whole and multiply by 100.
For change, always divide by the starting number. That is why a price that rises 50% and then falls 50% does not end where it began.
The formula behind it
- X% of Y = X ÷ 100 × Y
- X as a % of Y = X ÷ Y × 100
- % change = (new - old) ÷ old × 100
- Original from a part = part ÷ (percentage ÷ 100)
A worked example
A jacket costs $80 and is 15% off. 15% of 80 is 0.15 × 80 = 12, so you save $12 and pay $68. If a number grows from 40 to 50, the change is 10 and 10 ÷ 40 = 0.25, a 25% increase.
Questions people ask
Is a percentage change the same going up and down?
No. Going from 40 to 50 is +25%, but going from 50 back to 40 is -20%, because the starting number is different each time.
How do I take a percentage off a price?
Work out the percentage of the price, then subtract it. Or multiply by one minus the discount: 15% off means multiply by 0.85.
What is percentage points versus percent?
If a rate goes from 10% to 12%, it rose by 2 percentage points but by 20 percent in relative terms.
Can a percentage be more than 100?
Yes. 150% of a number is one and a half times that number.