How to Calculate Percentage Amount From Total Amount

April 24, 2025 4 min read

The term "percentage" comes from the Latin per centum, meaning "by the hundred." A percentage is essentially a fraction with 100 as the denominator. It represents the relationship between a part and a whole, where the whole is always considered to be 100. Calculating percentages is a fundamental skill with applications in many areas of life, from figuring out discounts and sales tax to understanding statistics and financial data.

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The Basic Percentage Formula

The most common way to calculate a percentage is by using the following formula:

Percentage = (Value / Total Value) * 100

Where:

  • Value: The specific quantity or amount you're interested in.
  • Total Value: The entire quantity or amount that includes the value.

This formula allows you to express a portion of a whole as a percentage.

Examples of Calculating Percentage Amount

Let's illustrate with a few examples:

  1. Example 1: You scored 85 out of 100 on a test. What's your percentage score?

    Percentage = (85 / 100) * 100 = 85%

  2. Example 2: A store offers a 20% discount on a shirt that originally costs $50. What is the discount amount?

    Here, we want to find what amount corresponds to 20% of $50, so we first calculate 20% = 20/100 = 0.2

    Discount Amount = 0.2 * $50 = $10

  3. Example 3: In a class of 40 students, 10 are girls. What is the percentage of girls?

    Percentage = (10 / 40) * 100 = 25%

Using Percentage Amount to Determine Value

Sometimes you want to calculate amount from a percentage. This is just as simple and involves a slight modification to the formulas. Here are a few examples:

  1. Example 1: A store offers 15% off all items, and you want to know how much you'll save on a $200 item.

    Amount = Percentage / 100 * Total Amount

    Amount = (15 / 100) * $200 = $30

Percentage Increase and Decrease

Percentages are also useful for calculating increases or decreases in value. The formula to calculate percentage change is:

Percentage Change = ((New Value - Original Value) / Original Value) * 100

A positive result indicates an increase, while a negative result indicates a decrease.

Example: A product's price increased from $80 to $100. What is the percentage increase?

Percentage Increase = (($100 - $80) / $80) * 100 = 25%

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While these calculations are straightforward, our percentage calculator makes it even easier! Whether you need to find a percentage of a number, determine the percentage one number is of another, or calculate percentage increase or decrease, our tool provides instant results. It's designed for simplicity and accuracy, saving you time and effort.

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Beyond the Basics

Understanding the basics opens the door to more complex calculations: