Percentage Calculator
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How to use Percentage Calculator
- Enter A and B.
- Read all three results.
- Change the numbers to try other cases.
Common uses
- Working out sale discounts and markups.
- Calculating growth or decline between two values.
- Checking exam scores.
About this tool
Three common percentage questions in one place: what A percent of B is, what percent A is of B, and the percentage change from A to B. Enter the two numbers and all three results update together. Percentage change is calculated as (B − A) ÷ A × 100.
Worked example
15% of 80 is 12 (80 × 0.15). Increasing 80 by 15% gives 92, and 12 is 15% of 80 because 12 ÷ 80 = 0.15.
Common problems and fixes
- Percent change versus percentage points.
- Going from 10% to 12% is a rise of 2 percentage points but a 20% increase.
- Increasing and decreasing do not cancel.
- Adding 20% and then subtracting 20% does not return to the start: 100 → 120 → 96.
- Which number is the base?
- “X is what percent of Y” divides by Y. Swapping them gives a different answer.
Next steps
Frequently asked questions
How do I find X% of Y?
Multiply Y by X and divide by 100.
How is percentage change calculated?
(new − old) ÷ old × 100.
Why can percentage change exceed 100%?
If the new value is more than double the old, the change is above 100%.
Are my files uploaded to a server?
No. Everything runs inside your browser on your own device, so your files and text are never sent anywhere.
Is it really free?
Yes. There is no sign-up, no watermark and no limit on how often you use it.
Does it work on my phone?
Yes. It works in any modern browser on phones, tablets and computers. Very large files may be slow on older phones.