Percentage Calculator
Perform various percentage calculations. Current mode: What is X% of Y?
Result will appear here.
What This Calculator Does
"Percentage" questions actually come in a few distinct shapes, and mixing them up is a common source of mistakes. This tool covers three of them separately: finding X% of a number, working out what percent one number is of another, and finding the percentage change between an old value and a new one — each with its own dedicated mode so you plug in the right numbers for the question you're actually asking.
How to Use It
Pick a Calculation Mode first, since it determines which two fields appear below it. "What is X% of Y?" asks for a Percentage Rate and a Base Value. "X is what % of Y?" asks for a Part Value and a Whole Value. "Percentage Change from X to Y" asks for an Old Value and a New Value, and reports the result as either an increase or a decrease depending on the sign — a drop in value shows as a decrease rather than a negative percentage.
The Formula
"What is X% of Y?" computes (Y × X) ÷ 100. "X is what % of Y?" computes (X ÷ Y) × 100. "Percentage Change from X to Y" computes ((Y − X) ÷ X) × 100, then the calculator takes the absolute value for display and labels it an increase or decrease based on whether the raw result was positive or negative.
A Worked Example
In "What is X% of Y?" mode, 20% of 50 gives (50 × 20) ÷ 100 = 10. Switch to "X is what % of Y?" mode and ask what percent 30 is of 150: (30 ÷ 150) × 100 = 20% — the same numbers as the first example, but rearranged to answer a different question. In "Percentage Change" mode, going from 100 to 120 is ((120 − 100) ÷ 100) × 100 = 20%, and the calculator reports this as a 20% increase; going the other direction, from 200 down to 150, is ((150 − 200) ÷ 200) × 100 = −25%, which the calculator reports as a 25% decrease.
How to Calculate Percentages Manually
For "X% of Y," turn the percentage into a decimal by dividing by 100 (20% becomes 0.20), then multiply by Y (0.20 × 50 = 10). For "X is what % of Y," divide X by Y and multiply by 100 (30 ÷ 150 = 0.2, then 0.2 × 100 = 20%). For percentage change, subtract the old value from the new one, divide by the old value, and multiply by 100 — a positive result is an increase, a negative result is a decrease (for example, (120 − 100) ÷ 100 = 0.2, times 100 is a 20% increase).
FAQ
- What percentage calculations can I do?
- Find X% of a number, what percent A is of B, percentage increase from A to B, and percentage decrease.
- How is percentage increase calculated?
- Percentage Increase = ((New Value − Old Value) ÷ Old Value) × 100.