About this tool
Three questions get called “percentage” and they are not the same sum. What is 12% of 4,500. Is 380 out of 600 a pass. Did the electricity bill go up by much this month. Each needs its own arrangement of the same two numbers, which is why picking the calculation comes before typing anything.
Percentage change is the one that trips people up, and negative numbers are why. The change here is measured against the size of the starting value with its sign ignored, so a balance moving from -50 to -25 is reported as a 50% rise rather than a 50% fall. Halving a debt is an improvement, and the answer should read like one.
Where a calculation would divide by zero the tool stops and tells you, instead of showing an infinity symbol you then have to interpret. Everything happens in the page: no request goes out, the numbers are not logged, and it works the same with mobile data switched off.
How to use this tool
- Pick the calculation. Three options: “What is A% of B?”, “A is what percent of B?”, and “Percentage change from A to B”. The two number fields mean different things in each one, so choose this first.
- Enter A and B. They start at 20 and 500, which under the default calculation asks what 20% of 500 is.
- Read the result. A single line. Large numbers are grouped Indian-style, so 1250000 comes back as 12,50,000.
What this tool does not do
- It does not add a percentage on top of a number. For a price after a discount, use the discount calculator.
- It has no GST, income tax or interest logic. It does plain percentage arithmetic.
- It does not work backwards from a result to the original figure.
- It gives percentages, not percentage points.
Common questions
What do A and B stand for?
It depends on the calculation. In “What is A% of B?” A is the rate and B is the amount, so 18 and 2,000 gives 360. In “A is what percent of B?” A is the part and B is the whole, so 45 and 60 gives 75%. In “Percentage change from A to B” A is where you started and B is where you ended up.
Why does it refuse to calculate?
Two cases would mean dividing by zero. Asking what percent A is of zero has no answer, and a percentage change away from zero has no answer either, because there is no starting size to compare against. In both the tool says so instead of showing infinity.
My starting number is negative. Is the change right?
Yes. The change is measured against the size of the starting value, ignoring its sign, so a move from -50 to -25 reads as a 50% rise. That matches how a loss shrinking is normally described.
Is a change of 5% the same as 5 percentage points?
No, and the difference matters. Going from 10% to 15% is a rise of 5 percentage points but a rise of 50%. This tool gives you the percentage, not the percentage points.
How precise is the answer?
It is worked out in full and displayed to at most eight decimal places, so a third of something shows as 33.33333333% rather than being quietly rounded to 33%.