Three questions, one page
Almost every percentage problem is one of three shapes: a part of a total, a share expressed as a percent, or a change between two numbers. All three are on this page and update as you type, so there is no switching between calculators.
Percentage change catches people out
Change is always measured against the starting number. Going from 50 to 100 is a 100% rise, but going back from 100 to 50 is a 50% fall, even though the gap is identical. This is why a stock that drops 50% needs a 100% gain to break even.
Quick mental shortcuts
- 10% is the number with the decimal point moved one place left.
- 5% is half of 10%, and 15% is 10% plus 5%.
- X% of Y always equals Y% of X, so 18% of 50 is the same as 50% of 18, which is 9.
Frequently asked questions
What is the difference between percentage change and percentage points?
Change compares two numbers relative to the first one. Percentage points are a plain subtraction, so a rate moving from 4% to 6% is a rise of 2 percentage points but a 50% increase.
Can I use negative numbers?
Yes. Percentage change uses the absolute value of the starting number, so the direction of the result still reads correctly.
Why does the result update without a button?
Every field is live, so you can adjust a number and read the new answer straight away.