Find a percentage of a number, what percentage one number is of another, and the percentage change between two numbers.
Try an example
Load a ready-made sample into this tool and run it. Every result you see is calculated live by the tool itself — nothing here is a pre-written answer.
Sample: a: 150; b: 200; p: 20
How to Use
- Enter the two numbers for your question.
- Read all three results.
- Use only the result that matches your question.
What this percentage calculator does
This percentage calculator answers the three everyday percentage questions in one place: what a given percent of a number is, what percent one number is of another, and how much a value changed in percent between an old figure and a new one. Enter the two numbers your question involves, read all three results, and use the one that matches what you asked.
The three formulas
Percent of a number multiplies the number by the percentage over 100: 20% of 80 is 80 × 0.20 = 16. One number as a percent of another divides the first by the second, then multiplies by 100. Percentage change divides the difference between the old and new values by the old value, then multiplies by 100.
Good to know
Percentage change is measured against the old value, so it cannot be calculated when the old value is zero — the calculator shows an error instead of inventing a figure. Also note that a rise of 50% followed by a fall of 50% does not return you to the start, because each change is applied to a different base.
Frequently asked questions
How do I find what percent 30 is of 120?
Divide 30 by 120 and multiply by 100, giving 25%. In this calculator that is the second result — one number as a percentage of another. The method suits any part-versus-whole question.
Why can percentage change not start from zero?
Change is the difference divided by the old value, and dividing by zero has no defined answer. From zero, any increase is effectively unbounded, so the calculator flags an error instead.
Is a percentage point the same as a percent?
No. A move from 10% to 12% is a rise of 2 percentage points but a 20% increase relative to the old rate. Reports often mix the two, so read quoted changes carefully.
How to use Percentage Calculator
- Enter the two numbers for your question.
- Read all three results.
- Use only the result that matches your question.
Limitations
Percentage change divides by the old value, so it is undefined when the old value is zero and an error is shown instead.