Percentage Calculator: % of a Number, Change and Difference

Percentage (X)

Number (Y)

Result

Visual Representation

15%85%

15%15%

85%85%

3:20

Your calculations will appear here

The Percentage Calculator helps you quickly find percentages, percentage changes, and percentage differences. Whether you need to calculate a tip, work out a discount, or find what percentage one number is of another, this tool handles it all.

Simply enter your values and get instant results. Choose a percentage of a number, what percentage one number is of another, percentage change, percentage difference or reverse percentage. Amounts can be typed as 25%, 1,200 or 12.5.

A percentage is a share of 100, so 15% of 240 sits at the same point on both bars: 36. Divide 36 by 240 and you are back at 15%.

How to Use the Percentage Calculator

Choose a calculation mode using the buttons at the top: find a percentage of a number, find what percentage one value is of another, calculate percentage change, calculate percentage difference, and reverse percentage.
Enter your values in the input fields. Labels update automatically to match the selected mode. Results are calculated in real time as you type.
Review the step-by-step working below the result to understand the method. The visual charts show the proportional relationship between your values.
Use the format toggle to switch between ratio, fraction, decimal, and percentage representations where available. Copy the share URL to save or send your calculation.

Formula and Theory

A percentage expresses a number as a fraction of 100. The term derives from the Latin "per centum", meaning "by the hundred". Percentages appear throughout daily life in contexts such as discounts, tax rates, interest, exam scores, and statistical analysis.

Each percentage operation serves a distinct purpose. "X% of Y" converts the percentage to a decimal and multiplies. "What % is X of Y" divides the part by the whole and multiplies by 100. "Percentage change" measures how much a value has increased or decreased relative to its original. "Percentage difference" compares two values symmetrically using their average as the base. "Reverse percentage" finds the original whole when you know a part and what percentage it represents.

Percentage change can be positive (increase) or negative (decrease) and uses the absolute value of the original as the denominator. Percentage difference is always non-negative because it uses the absolute difference divided by the absolute average, making it useful when neither value is clearly the "original".

Worked Examples

Example 1: Finding a percentage of a number

Problem: What is 15% of 240?

Solution: Convert 15% to a decimal: 15 / 100 = 0.15. Multiply: 0.15 * 240 = 36.

Answer: 36

Example 2: Finding what percentage one number is of another

Problem: What percentage is 45 of 180?

Solution: Divide the part by the whole: 45 / 180 = 0.25. Multiply by 100: 0.25 * 100 = 25.

Answer: 25%

Example 3: Calculating percentage change

Problem: A product price rose from 80 to 100. What is the percentage change?

Solution: Difference: 100 - 80 = 20. Divide by original: 20 / 80 = 0.25. Multiply by 100: 0.25 * 100 = 25.

Answer: 25% increase

Example 4: Calculating percentage difference

Problem: What is the percentage difference between 40 and 60?

Solution: Absolute difference: |40 - 60| = 20. Average: (40 + 60) / 2 = 50. Divide: 20 / 50 = 0.4. Multiply by 100: 0.4 * 100 = 40.

Answer: 40%

Example 5: Reverse percentage

Problem: 36 is 15% of what number?

Solution: Convert 15% to a decimal: 15 / 100 = 0.15. Divide: 36 / 0.15 = 240.

Answer: 240

Frequently Asked Questions

How do I calculate a percentage of a number?

Divide the percentage by 100 to get a decimal, then multiply by the number. For example, 20% of 150 is (20 / 100) * 150 = 30.

What is the difference between percentage change and percentage difference?

Percentage change measures the increase or decrease from a specific original value and can be positive or negative. Percentage difference compares two values symmetrically, using their average as the base, and is always non-negative.

Can a percentage be greater than 100%?

Yes. A percentage above 100% means the part exceeds the whole. For instance, if a value rises from 50 to 150, the percentage change is 200%.

What is a reverse percentage calculation?

A reverse percentage finds the original whole when you know a part and the percentage it represents. If 36 is 15% of a number, divide 36 by 0.15 to get 240.

How do I convert a fraction to a percentage?

Divide the numerator by the denominator and multiply the result by 100. For example, 3/4 = 0.75, and 0.75 * 100 = 75%.

Why does percentage change use the absolute value of the original?

Using the absolute value ensures the formula works correctly when the original value is negative. Without it, a change from -50 to 0 would produce a negative percentage, which would be misleading.

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