How to Use the Percentage Calculator
Percentages appear everywhere. In sales, grades, statistics, and finance. This calculator handles the three most common percentage calculations instantly.
Step-by-Step Instructions
- 1 Choose the calculation type: find percentage, find what percent, or percentage change.
- 2 Enter the known values.
- 3 Click calculate to see the result.
Understanding the Inputs
Mode
Selects the type of percentage calculation you want to perform. The three modes are "X% of Y" (find a percentage of a number), "what percent of Y is Z" (find what percentage one number is of another), and "X% of what is Z" (find the whole given a percentage part). For example, choose "X% of Y" to calculate a 15% tip on a $60 meal.
How to find it: Choose the mode from the dropdown at the top of the calculator. The label above the dropdown clearly states "Mode" and the three options are listed for you to pick from.
Why it matters: The mode tells the calculator which value to solve for. Selecting the wrong mode will give you a mathematically correct answer to the wrong question, so matching the mode to your real world scenario is essential for getting useful results.
Type: select · Default: of
Percentage (X)
The percentage value you want to use in the calculation. In "X% of Y" mode, this is the percentage rate (e.g., 15 for 15%). In "what percent of Y is Z" mode, this is the result you are solving for. For a 7% sales tax calculation on a $200 purchase, enter 7 here.
How to find it: Enter the percentage as a plain number. Do not include the percent sign. If a store advertises 20% off, enter 20. This value comes directly from the percentage mentioned in your problem.
Why it matters: The percentage value X is one of the three variables in any percentage equation. Without it, the calculator cannot determine the proportion you are trying to find.
Type: number · Default: 0
Number (Y)
The original or base number that the percentage is applied to or compared against. In "X% of Y" mode, this is the whole amount (e.g., $200 for a purchase). In other modes, it is the number you are comparing something to. For a 20% discount on a $250 jacket, enter 250 here.
How to find it: Look at the total or starting value in your scenario. For a shopping discount, this is the original price before the discount. For a test score, this is the total points possible. Enter it as a plain number.
Why it matters: Y represents the whole or the reference value. Percentages are always relative to a base number, so without Y, the calculator cannot compute what the percentage represents in absolute terms.
Type: number · Default: 0
New Value (Z)
The resulting or partial value after applying a percentage. In "what percent of Y is Z" mode, this is the part you are comparing to the whole. In "X% of what is Z" mode, this is the resulting value you already know. For example, if you scored 85 out of 100, enter 85 here.
How to find it: This is the actual amount you have or want to achieve. For a test score, it is your points earned. For a sale price after discount, it is what you actually paid. Enter the number exactly as it appears.
Why it matters: Z completes the percentage equation as the third variable. Depending on the mode, Z is either the result being calculated or a known value used to find the missing percentage or base number.
Type: number · Default: 0
Tips & Best Practices
- ✓ For tip calculations, 15% = multiply by 0.15, 20% = multiply by 0.20.
- ✓ Percentage change = (New - Old) / Old x 100. Positive means increase.
- ✓ $ off discounts: multiply the original price by the decimal form of the percentage.
by CalculatorPro Tools · Updated 2026-07-29