How to Use
Enter Value A and Value B in the input fields.
Select the primary mode that matches your main question. This controls which result gets the large featured display.
Click Calculate. All five results appear simultaneously: percent of, ratio, change, point difference, and reverse ratio.
Use the Reset button to clear the fields and start a new calculation.
How the Three Formulas Work
Three formulas run on every calculation. A% of B multiplies B by A divided by 100, which is useful for discounts, tips, or finding a share of a total. A is what percent of B divides A by B and multiplies by 100, expressing one value as a proportion of another. Percentage change from A to B subtracts A from B, divides by the absolute value of A, then multiplies by 100 to show growth or decline relative to the starting point. The percentage point difference is the raw subtraction B minus A, and the reverse ratio shows B as a percentage of A to complement the second formula.
Worked Example: Sale Price
- A product costs 80 and is on sale for 60. Enter A = 80, B = 60.
- A% of B: 80% of 60 = 48. Not directly useful here, but shown for completeness.
- A is what % of B: 80 is 133.33% of 60. The original price is 133.33% of the sale price.
- Percentage change from 80 to 60: (60 minus 80) / 80 x 100 = negative 25%. The discount is 25%.
- Difference (B minus A): 60 minus 80 = negative 20.
- B as % of A: 60 / 80 x 100 = 75%. The sale price is 75% of the original.
When to Use This Calculator
- Calculating a tip or service charge as a percentage of a bill
- Finding the discount amount when a price drops by a given percent
- Comparing two values to see which is the larger or smaller proportion
- Measuring growth or decline between two time periods for sales, scores, or metrics
- Converting a fraction to a percentage for a report or presentation
- Checking how much a rate changed in percentage points between two periods
Division by Zero
Percentage change requires Value A to be non zero because it is the denominator. When A equals zero the result is shown as undefined. The ratio A as a percent of B also requires B to be non zero. All other results remain valid regardless of input values.
Percentage vs. Percentage Points
Key Features
Five Results From Two Inputs
Every calculation runs simultaneously so you never need to switch modes or re-enter numbers to see a different result.
Three Core Formulas
Covers the three most searched percentage questions: percent of a value, ratio between values, and percentage change.
Percentage Point Difference
Shows the arithmetic difference B minus A, which matters when comparing two rates like tax brackets or poll results.
Reverse Ratio
Displays B as a percentage of A alongside A as a percentage of B, giving both directions of the comparison.