Percentage Calculator

Using this percentage calculator is simple. Start by selecting one of the three calculation modes from the dropdown menu, then enter your two numbers:

1. Mode: "What is X% of Y?" – Use this to find a percentage of a number. Enter the percentage as Number A and the base number as Number B. For example, to find 20% of 250, enter A = 20 and B = 250. The calculator returns 50.
2. Mode: "X is what % of Y?" – Use this to determine what percentage one number represents of another. Enter the part as Number A and the whole as Number B. For example, to find what percent 36 is of 150, enter A = 36 and B = 150. The calculator returns 24%.
3. Mode: "% change from X to Y" – Use this to calculate how much a value has increased or decreased in percentage terms. Enter the original value as Number A and the new value as Number B. For example, to find the percentage change from 80 to 100, enter A = 80 and B = 100. The calculator returns 25% increase.

Results appear instantly as you type or change inputs. The calculator also displays a plain-language description of the calculation so you can verify you are computing the right thing. You can switch between modes at any time without losing your entered values, making it easy to explore different percentage relationships with the same numbers.

A percentage calculator is a versatile math tool that solves the three most common types of percentage problems. Percentages, meaning "parts per hundred," are one of the most widely used mathematical concepts in everyday life. The symbol % represents a fraction with a denominator of 100, so 25% is simply another way of writing 25/100 or 0.25.

The three fundamental types of percentage problems this calculator handles are: (1) finding X% of a number Y, such as calculating 20% of $150 to determine a tip or discount; (2) determining what percentage one number is of another, such as figuring out what percent 45 is of 60 on a test score; and (3) computing the percentage change between two values, such as tracking how much a stock price has risen or fallen.

Percentages appear in nearly every aspect of daily life and professional work. When shopping, you encounter percentages as sales tax rates, discount amounts, and credit card interest rates. In school, test scores and grades are often expressed as percentages. In finance, percentages describe investment returns, inflation rates, mortgage interest, and profit margins. In health and science, percentages are used for body fat composition, probability calculations, and statistical data analysis. Even cooking uses percentages when scaling recipes up or down.

Understanding how to work with percentages is an essential life skill. This calculator eliminates the need for manual arithmetic by providing instant, precise results for all three calculation types in a single, easy-to-use interface. Whether you are a student checking homework, a shopper comparing deals, or a professional analyzing business metrics, this tool saves time and ensures accuracy.

The three percentage formulas used in this calculator are shown below, along with the method for converting between fractions, decimals, and percentages:

• Percentage of a number: Result = (A / 100) × B. This converts the percentage to a decimal by dividing by 100, then multiplies by the base number.
• What percent is A of B: Result = (A / B) × 100. This divides the part by the whole to get a decimal, then multiplies by 100 to express it as a percentage. Division by zero returns an error.
• Percentage change: Result = ((B − A) / |A|) × 100. This computes the difference between new and old values, divides by the absolute value of the original, and multiplies by 100. A positive result indicates an increase; a negative result indicates a decrease.

To convert between forms: a fraction like 3/4 becomes a decimal (0.75) by dividing the numerator by the denominator, and becomes a percentage (75%) by multiplying the decimal by 100. Conversely, to convert a percentage to a decimal, divide by 100 (e.g., 45% = 0.45), and to convert a decimal to a fraction, express it over the appropriate power of 10 and simplify (e.g., 0.75 = 75/100 = 3/4).

Example 1 – Calculating a Restaurant Tip: You want to leave a 18% tip on a $75.00 dinner bill. Select "What is X% of Y?" mode, enter A = 18 and B = 75. The calculator shows: 18% of 75 is 13.50. So your tip is $13.50, making the total bill $88.50. This is the most common percentage calculation people perform in everyday life.

Example 2 – Finding a Test Score Percentage: A student answered 42 questions correctly out of 50 on an exam. To find the percentage score, select "X is what % of Y?" mode, enter A = 42 and B = 50. The calculator shows: 42 is 84% of 50. The student scored 84% on the exam, which is typically a B grade.

Example 3 – Tracking a Price Change: A laptop was priced at $899 last month and is now listed at $749. To find the percentage change, select "% change from X to Y" mode, enter A = 899 and B = 749. The calculator shows: the percentage change from 899 to 749 is -16.69% (decrease). This tells you the laptop price dropped by about 16.7%, helping you evaluate whether the deal is significant enough to buy now.

Example 4 – Calculating Sales Tax: You want to know how much sales tax you will pay on a $45.00 purchase with an 8.25% tax rate. Select "What is X% of Y?" mode, enter A = 8.25 and B = 45. The result is 3.7125, meaning you will pay approximately $3.71 in sales tax for a total of $48.71.