What this percentage calculator does
This is four calculators in one. Pick a mode and fill in two numbers — the answer updates instantly:
- Percent of a value — what is 25% of 200?
- What percent — 50 is what percent of 200?
- Percentage change — how much did a value rise or fall from A to B?
- Increase / decrease — add or subtract a percentage from a value.
For every result the calculator shows the calculation steps: the answer as a sentence, the formula with your numbers filled in, and the difference. Everything is calculated locally in your browser.
The formulas behind it
| Question | Formula | Example |
|---|---|---|
| P% of N | N × P ÷ 100 | 25% of 200 = 50 |
| X is what % of Y | X ÷ Y × 100 | 50 of 200 = 25% |
| Change A → B | (B − A) ÷ A × 100 | 100 → 150 = +50% |
| N changed by P% | N × (1 + P ÷ 100) | 200 + 25% = 250 |
For increase/decrease, enter a negative percentage to subtract — for example −10% turns 200 into 180.
Where you will use it
- Shopping — a 30% discount off a price, or VAT added on top. In Germany, Section 12 of the VAT Act (UStG) sets a standard rate of 19% and a reduced rate of 7% — both jobs for the “increase” mode.
- Finance — interest, tips, growth from one figure to another.
- Work and study — test scores, conversion rates, year-on-year change.
- Everyday maths — splitting bills, comparing before-and-after numbers.
Showing the steps and sharing a result
Below the result you get the calculation steps: first the sentence you can pass on (“50 is 25% of 200”), then the formula with your numbers filled in, and for changes also the difference. One click copies all lines. The mode and both numbers are also reflected in the address bar — copy the link, and the recipient opens exactly the same calculation.
A note on percentage change
Percentage increase and decrease are not symmetric. If a price rises 50% and then falls 50%, you do not return to the start: 100 → 150 → 75. That is why the “percentage change” mode always measures relative to the starting value.
Privacy
The calculator runs entirely in your browser. Nothing is uploaded; your last mode and entries are stored locally so the tool opens where you left it. Only if you pass the link on yourself does the recipient see the numbers in it.