Percentage Calculator

What is a Percentage?

A percentage is a way of expressing a number as a fraction of 100. The word itself comes from the Latin "per centum," meaning "by the hundred." When you see 25%, it simply means 25 out of every 100. Percentages are used everywhere in daily life, from sales discounts and tax rates to exam scores and statistical data.

The Percentage Formula

• What is X% of Y? for finding a discount, tip, or share of a total.
• X is what percent of Y? for turning a part and a whole into a percentage.
• Percentage change for measuring how much a value went up or down.

Pick the question that matches your situation, type in your numbers, and press Calculate.

How to use this calculator

1. Choose the type of percentage problem, such as finding a percent of a number or finding percent increase or decrease.
2. Enter the given values, such as the part and whole, or the starting and ending amounts.
3. Check that your numbers match the question, because order matters in percent increase and decrease.
4. Read the result as a percent, then use it to interpret the comparison or change.

The formula explained

The formula \(\text{Percentage} = \frac{\text{Part}}{\text{Whole}} \times 100\) computes how many out of 100 the part represents. For increase and decrease, the same idea compares the change to the original amount.

• Part = the smaller amount or the amount being compared
• Whole = the total amount or original amount used as the reference
• Percentage = the result written as a percent

Step by step method

1. Divide the part by the whole to make a decimal.
2. Multiply the decimal by 100 to convert it to a percent.
3. For increase or decrease, first find the change, then divide that change by the original amount and multiply by 100.
4. Check whether the result should be labeled as an increase or a decrease.

Worked example

Problem. A student answered 18 questions correctly out of 24 on a quiz. What percent of the quiz did the student answer correctly?

1. Use the formula: \(\frac{18}{24} \times 100\).
2. Compute \(18 \div 24 = 0.75\).
3. Multiply by 100: \(0.75 \times 100 = 75\).

Tips and common mistakes

• Make sure the whole is the original total, not the part you want to compare.
• For percent change, use the original value as the whole, not the new value.

Frequently asked questions