Percentage Calculator
Perform various percentage calculations (X of Y, percentage change, increase/decrease).
Percentage Calculator workspace
Parameters Configuration
Ready for calculations
Configure parameters on the left and press Calculate.
Using Percentage Calculator
Select Calculation: Choose a percentage calculation type from the dropdown.
Enter Inputs: Fill in the numeric base values in the secure forms.
Inspect Output: Read the calculated percentage values in real-time.
Copy Output: Copy the computed percentage output to your clipboard.
Calculate percentage changes, fractional margins, and proportional increases. The calculator maps ratio differences onto clear percent values, enabling quick commercial markup analysis in browser memory.
Five distinct questions get called "percentage", and they have five different formulas. Picking the wrong one produces an answer that looks plausible and is not. The mode selector at the top of the form names each question in plain language so you cannot pick by accident.
The five modes
| Mode | Question | Formula |
|---|---|---|
| Percent of | What is A% of B? | A ÷ 100 × B |
| Is what percent of | A is what percent of B? | A ÷ B × 100 |
| Percent change | From A to B, what changed? | (B − A) ÷ A × 100 |
| Increase by | A increased by B% | A × (1 + B ÷ 100) |
| Decrease by | A decreased by B% | A × (1 − B ÷ 100) |
Worked briefly: 37 as a percentage of 160 is 23.13%. Going from 250 to 190 is a 24% decrease. Increasing 1,450 by 12% gives 1,624.00; decreasing it by 12% gives 1,276.00.
Percentage change does not reverse
Going from 250 down to 190 is a 24% fall. Going back from 190 to 250 is a 31.58% rise. The two are not the same because each is measured against a different starting figure.
The increase and decrease modes carry the same asymmetry. Add 12% to 1,450 and you get 1,624. Take 12% off 1,624 and you get 1,429.12, not 1,450. To undo an increase you divide by 1.12; to undo a decrease you divide by 0.88. Subtracting the same percentage is the reliable way to end up with the wrong number, and it is exactly how people mis-remove tax from a gross figure.
The general point: a 50% fall requires a 100% rise to recover.
Zero denominators are rejected, not fudged
Two of the modes divide by a value you supply, and zero has no sensible answer there.
Asking what 40 is as a percentage of 0 returns an explanation rather than a number, because nothing is a percentage of zero. Asking for the change from 0 to 50 does the same, because any increase from nothing is undefined rather than infinite. Returning 0 for either would be a specific false answer rather than an absent one, which is why neither does.
Percent and percentage point are different words
The tool does not distinguish these, so you must.
If an interest rate moves from 4% to 5%, that is a rise of one percentage point and a rise of 25 percent. Both statements are true and they describe the same event with very different force. Financial and political writing uses them interchangeably and incorrectly all the time. When you are comparing two rates, subtract them for the percentage-point gap and use the percent change mode for the relative one — and say which you mean.
Where this page lives
The percentage calculator now sits under calculators rather than converters, which is where it always belonged. Its five modes cover the arithmetic behind most of the other tools on the site: tax rates, discounts, margins, growth rates and interest are all percentage operations with domain-specific labelling.
Related growth and return tools
For percentage change applied to revenue across several years, use the revenue growth calculator. For a reduction off a price, with stacking explained, use the discount calculator. For profit expressed as a share of price rather than cost, use the profit margin calculator.
Frequently asked
How do I calculate percentage increase?
Calculate percentage increase by subtracting the original value from the new value, dividing the difference by the original value, and multiplying by 100.
Can I convert fraction values to percentages?
Yes, the tool has an option to calculate what percentage one number is of another, which is the same as converting a fraction.
Are my math inputs secure?
Yes, all calculation logic runs locally inside browser memory.