Percentage Calculator
Work out percentages, increases, decreases and what-of-what — three calculators in one.
What is the Percentage Calculator?
The Percentage Calculator answers the three most common percentage questions in separate modes: "What is X% of Y?", "A is what percent of B?" and "What is the percentage change from old to new?". Results update live as you type.
Each mode chooses the correct formula and labels the required values, reducing a common source of mistakes: confusing a percentage of a number with the percentage difference between two numbers. The change mode preserves the sign, so a fall from 80 to 60 appears as a decrease rather than an unsigned difference.
Calculations run in your browser, so real salaries, scores and budgets never leave your device. The fields are unit-neutral; the same calculation works for dollars, kilograms, survey responses, test marks or any other values measured on the same basis.
How to use the Percentage Calculator
- 1Pick a mode from the tabs at the top.
- 2For "X% of Y", enter the percentage and the amount.
- 3For "A is what % of B", enter the partial value and the total.
- 4For "% change", enter the original and new values.
- 5The result appears below the inputs as soon as you finish typing.
When to use the Percentage Calculator
- Find the tax, tip or commission represented by a percentage of an amount.
- Calculate what percentage of a class passed, responded or completed an assignment.
- Measure revenue, traffic or price growth between an old and a new reporting period.
- Convert a score such as 42 out of 50 into a percentage for comparison.
Key features
- Three modes: percent-of, is-what-percent-of, percent-change
- Live recalculation on every keystroke
- Handles negative changes (decreases show as negative %)
- Works with any currency or unit
Frequently asked questions
How do I calculate a percentage increase?
Use "% change" mode: enter the original value first and the new value second. Positive means increase, negative means decrease.
How is the calculation done?
X% of Y: (X ÷ 100) × Y. A of B: (A ÷ B) × 100. Change: ((new − old) ÷ old) × 100.
Can percentages be greater than 100?
Yes. For example, 150% of 40 is 60, and a value that rises from 40 to 100 has increased by 150%. The tool does not restrict valid percentages to the 0–100 range.
Why is percentage change undefined when the old value is zero?
The formula divides the difference by the original value. Division by zero has no finite result, so there is no conventional percentage change from a zero baseline.
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