Percentage Calculator: Calculate Percentages and Percentage Change Online

What Is a Percentage?

A percentage is a ratio expressed as a fraction of 100. The word comes from the Latin 'per centum' meaning 'per hundred.' A 25% value means 25 out of every 100 — or equivalently, the decimal 0.25.

The three main calculations people need are: (1) X is what percent of Y, (2) what is X% of Y, and (3) what is the percentage change from X to Y. Each has a different formula, which is why a dedicated tool prevents mistakes.

• Basic percentage: X / Y × 100 = percent
• Percentage of a number: (percent / 100) × number = result
• Percentage change: ((new - old) / old) × 100 = % change
• Reverse percentage: finding the original value before a percentage was applied

How to Use This Tool

Select the calculation type from the tabs, fill in the known values, and the result appears immediately.

1. 1

   Choose a calculation mode

   Select from: 'X is what % of Y', '% of a number', or 'percentage change'.

2. 2

   Enter the known values

   Fill in the input fields for your chosen mode.

3. 3

   Read the result

   The answer appears instantly below the inputs.

4. 4

   Copy the result

   Click the copy button to copy the value to your clipboard.

5. 5

   Try another calculation

   Change any input and the result updates in real time.

Common Use Cases

Percentage calculations come up in almost every professional context.

• Discounts: calculate how much money you save on a 30% off sale
• Grade calculations: determine what percentage score you need on a final exam
• Financial growth: calculate revenue percentage change quarter over quarter
• Tax calculations: find the tax amount on a pre-tax price
• Data analysis: express counts as percentages of a total for charts and reports
• Tip calculation: find 18% or 20% of a restaurant bill

Tips and Best Practices

A few reminders to avoid the most common percentage mistakes.

• Percentage change is not symmetric: a 50% drop followed by a 50% rise does not return to the original value
• When reversing a percentage (removing a markup), divide by (1 + rate), not subtract the rate
• Percentage points and percentages are different: going from 2% to 3% is a 1 percentage point increase, but a 50% relative increase
• Always check which base the percentage is relative to — the same number looks very different as a % of different totals

Frequently Asked Questions