How to calculate a percentage

Calculating a percentage involves finding a fraction of a whole amount or comparing a part to the whole. The basic formula for calculating a percentage is:

Percentage (%) = (Part / Whole) x 100

Here’s a step-by-step guide on how to calculate a percentage:

  1. Identify the Part and the Whole: Determine what you want to calculate a percentage of. The “part” is the portion of the whole that you’re interested in, and the “whole” is the complete quantity or the total.
  2. Convert the Percentage to a Decimal (optional): If you are given a percentage as a decimal, you can convert it by dividing by 100. For example, 25% as a decimal is 0.25.
  3. Plug the Values into the Formula: Insert the values into the formula:
    • If you have the part and want to find the percentage of the whole: Percentage (%) = (Part / Whole) x 100
    • If you have the whole and want to find the percentage of the part: Percentage (%) = (Part / Whole) x 100
  4. Perform the Calculation: Calculate the percentage using the formula. Multiply the fraction by 100 to express it as a percentage.

    For example, if you have 25 out of 100, to find the percentage:

    Percentage (%) = (25 / 100) x 100 Percentage (%) = 0.25 x 100 Percentage (%) = 25%

So, in this case, 25 out of 100 is 25%, which means 25% of the whole.

Here are some common examples of percentage calculations:

  • Calculating a Discount: If an item is on sale for 20% off its original price, you’d calculate the new price by multiplying the original price by (1 – 0.20) or 0.80.
  • Determining a Grade Percentage: If you got 45 points out of 60 on a test, your grade percentage is (45 / 60) x 100, which simplifies to 75%.
  • Calculating Tax: If you need to add 8% sales tax to a $50 purchase, you’d add $50 x 0.08 = $4 in tax, making the total cost $54.

Calculating percentages is a fundamental mathematical skill used in various real-life scenarios.