Percentage Calculator: 5 Modes & Formulas
Choose the right percentage calculation
SimplyUtils provides five percentage operations. They answer different questions: a percentage of a number gives a part, a percentage change compares two values, and a reverse percentage finds the original whole. Select the matching tab, enter both values, and read the formula beneath the result. Each tab retains its inputs while this page is open.
Worked examples for every mode
| Tab | Inputs | Calculation | Result |
|---|---|---|---|
| X% of Y | 15 and 200 | 15 / 100 * 200 | 30 |
| What % is X of Y? | 30 and 200 | 30 / 200 * 100 | 15% |
| % Change | 100 to 120 | (120 - 100) / 100 * 100 | +20% |
| Reverse % | 30 is 15% of a whole | 30 / (15 / 100) | 200 |
| Increase / Decrease | 200 and 15 | 200 * 1.15; 200 * 0.85 | 230; 170 |
Common interpretation mistakes
A discount amount and a discounted price are different results. For a price of 200 and a 15% discount, X% of Y gives the amount removed, 30. The decrease result gives the remaining price, 170. Enter numbers without a currency symbol; this calculator does not convert currencies.
Percentage points also differ from percentage change. Moving from 20% to 25% is a rise of 5 percentage points, but entering 20 and 25 in the change tab returns +25%. That result is the relative increase compared with the original 20.
The change tab divides by the absolute value of the original. For example, -100 to -80 returns +20%, describing a numerical increase. Negative baselines can make financial interpretations ambiguous; check whether this convention fits your comparison.
Invalid inputs and rounding
Both inputs are required. A total of zero in the percent-of-total tab, a percentage of zero in the reverse tab, or an original value of zero in the change tab has no defined result. The calculator shows an explanation and removes the copy action for that result. Zero remains valid for ordinary multiplication: 0% of 200 is 0.
Results use floating-point arithmetic and display up to 10 significant digits, with trailing zeros removed. Very large results can exceed the numeric range and produce an error. Tiny values and long decimal fractions can lose precision. This is a general arithmetic aid, not an exact decimal accounting engine.
Processing and privacy
The calculation code runs in your browser without an API request or saved calculation history. Reloading the page clears the inputs. Copy sends the displayed result to your device's clipboard. The site's general analytics and cookie practices are described in the Privacy Policy.
For a different task, use the digit-sum calculator or the work-hours calculator.
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