The percentage formula helps convert a part of a total into a value out of 100. It is one of the most useful formulas in everyday maths because it appears in discounts, scores, business metrics, finance, growth rates, and comparisons.
Use the calculator to check the number quickly, then read the guide for formulas, examples, and common mistakes.
What the Percentage Formula Shows
The percentage formula shows how large one value is compared with another value.
It converts that relationship into a number out of 100, which makes the result easier to read and compare.
For example, saying 18 out of 60 can be less clear than saying 30%.
The Main Percentage Formula
The main formula is: percentage = part ÷ whole × 100.
The part is the amount being measured. The whole is the total amount.
If the part is 45 and the whole is 150, the percentage is 45 divided by 150 multiplied by 100, which equals 30%.
Part, Whole, and Percentage
Most percentage problems include three ideas: part, whole, and percentage.
If you know the part and the whole, you can calculate the percentage. If you know the percentage and the whole, you can calculate the part.
This is why understanding the relationship is more useful than memorising only one example.
Example: Percentage From Part and Whole
Suppose 12 out of 48 orders were returned.
The part is 12 and the whole is 48. The calculation is 12 ÷ 48 × 100.
The result is 25%. So 25% of the orders were returned.
Formula for Percentage of a Number
When you need to find a percentage of a number, the formula changes slightly.
The formula is: amount = number × percentage ÷ 100.
For example, 18% of 250 is 250 × 18 ÷ 100, which equals 45.
Formula for Finding the Whole
Sometimes you know the part and the percentage, but you need to find the whole.
The formula is: whole = part ÷ percentage × 100.
For example, if 30 is 20% of a number, the whole is 30 ÷ 20 × 100, which equals 150.
Percentage Formula in Discounts
Discount calculations use the percentage of a number formula.
If a product costs 200 and the discount is 15%, the discount amount is 200 × 15 ÷ 100, which equals 30.
Then the sale price is 200 - 30, which equals 170. For the full discount process, read Discount Formula.
Percentage Formula in Business Metrics
Businesses use percentages for profit margin, markup, conversion rates, refund rates, sales growth, and cost changes.
For example, profit margin is profit divided by revenue multiplied by 100. Markup is markup amount divided by cost multiplied by 100.
This is why percentage formulas connect naturally with the Profit Margin Calculator and Markup Calculator.
Common Mistakes With the Formula
One common mistake is dividing by the part instead of the whole. The whole should be the total value.
Another mistake is forgetting to multiply by 100 after dividing.
A third mistake is comparing percentages that use different base numbers. A percentage is only meaningful when the base is clear.
Use the Calculator
Use the Percentage Calculator to quickly calculate a percentage of a number.
For the broader explanation, read How to Calculate Percentage.
The calculator is best for quick answers, while the article helps you understand which formula to use.
Conclusion
The main percentage formula is part divided by whole multiplied by 100.
Once you understand part, whole, and percentage, you can solve many different percentage questions, including discounts, scores, changes, and business calculations.
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FAQs
What is the percentage formula?
Percentage = part divided by whole multiplied by 100.
How do I find a percentage of a number?
Use amount = number multiplied by percentage divided by 100.
How do I find the whole from percentage?
Use whole = part divided by percentage multiplied by 100.
What is the most common percentage mistake?
The most common mistake is using the wrong base number as the whole.