Ever find yourself staring blankly when asked to calculate percentages? You’re not alone! Percentages are everywhere, from discounts at your favorite store to test scores at school. Understanding how to calculate them can save you time and confusion.
In this quick guide, you’ll learn how to calculate percentages clearly and simply.
What You’ll Need
- A calculator (optional, but handy)
- Basic math skills (addition, multiplication, division)
Step 1: Understand What a Percentage Means
Percentage simply means “per hundred.” It tells you how many out of 100 parts something is.
- Example: 25% means 25 out of 100.
Step 2: Convert the Percentage to a Decimal
To calculate percentages, start by converting the percentage number to a decimal by dividing by 100.
- Formula:
Decimal = Percentage ÷ 100 - Example:
To convert 30% to decimal:30 ÷ 100 = 0.30
Step 3: Calculate the Percentage of a Number
Now multiply the decimal by the number you’re calculating the percentage of.
- Formula:
Result = Decimal × Number - Example:
What is 20% of 50?Decimal: 20 ÷ 100 = 0.20 Result: 0.20 × 50 = 10Answer: 20% of 50 is 10.
Step 4: How to Find Out What Percentage One Number Is of Another
Sometimes you’ll need to find out what percentage one number is of another. To do this, divide the first number by the second, then multiply by 100.
- Formula:
Percentage = (First Number ÷ Second Number) × 100 - Example: What percentage is 15 of 60?
(15 ÷ 60) × 100 = 25%Answer: 15 is 25% of 60.
Step 5: How to Calculate Percentage Increase or Decrease
To find the percentage change between two numbers, use the formula:
- Formula:
Percentage Change = [(New Number – Original Number) ÷ Original Number] × 100 - Example: If a product price goes from $40 to $50:
[(50 – 40) ÷ 40] × 100 = 25%Answer: The price increased by 25%.
Real-world Example
Suppose you’re shopping and see a shirt originally priced at $80 on sale for 30% off.
- Calculate the discount:
30% of 80 = 0.30 × 80 = $24 - Calculate final price:
80 – 24 = $56
You’ll pay $56 for the shirt.
Common Mistakes to Avoid
- Forgetting to convert percentage to decimal (always divide by 100).
- Mixing up original and new numbers in percentage change formulas.
FAQ (Frequently Asked Questions)
What is a quick way to calculate 10% of a number?
Simply move the decimal point one place to the left. For example, 10% of 200 is 20.
Can you calculate percentages without a calculator?
Absolutely! Practice simple percentages (10%, 25%, 50%) in your head for quick estimates.
