How to Calculate Percentage: Simple Formulas & Examples

Percentages run through everyday life — marks, discounts, tips, interest and statistics — yet "what's 15% of 2,400?" or "30 out of 50 is what percent?" still trips people up. This guide shows you how to calculate percentage the simple way: the handful of formulas that cover almost every situation, each with a clear worked example you can follow in seconds.

It's written for students, shoppers, small business owners and anyone who wants percentage math to feel effortless.

Key Concepts: What a Percentage Is

A percentage is a number out of 100. "Per cent" literally means "per hundred," so 25% is 25/100 = 0.25. Converting a percentage to a decimal (divide by 100) or a decimal to a percentage (multiply by 100) is the foundation of every calculation below.

The three questions you'll actually ask

• What is X% of Y? (e.g. 18% of 5,000)
• X is what percent of Y? (e.g. 30 out of 50)
• What's the percentage change? (old → new)

Identifying which question you're asking is more than half the battle.

In short: To find X% of a number, multiply by X/100. To express one number as a percentage of another, divide and multiply by 100.

The Core Percentage Formulas

X% of Y       = (X ÷ 100) × Y
X is what % of Y = (X ÷ Y) × 100
% change      = ((New − Old) ÷ Old) × 100

For increases and decreases specifically, see Percentage Increase Formula and Percentage Decrease Formula.

Step-by-Step: How to Calculate a Percentage

Find X% of a number

1. Convert the percentage to a decimal: 15% → 0.15.
2. Multiply by the number: 0.15 × 2,400 = 360.

Find what percent one number is of another

1. Divide: 30 ÷ 50 = 0.6.
2. Multiply by 100: 60%.

Or skip the steps with the Percentage Calculator.

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Real-World Examples

Example 1 — A discount

15% off ₹2,400: 0.15 × 2,400 = ₹360 saved → pay ₹2,040. More in Discount Percentage Calculation.

Example 2 — A test score

38 out of 50: (38 ÷ 50) × 100 = 76%. See Exam Percentage Calculator.

Example 3 — A tip

12% tip on ₹1,840: 0.12 × 1,840 = ₹220.80.

Common Mistakes to Avoid

1. Forgetting to divide the percentage by 100 before multiplying.
2. Swapping the numbers in "X is what % of Y" — divide the part by the whole.
3. Confusing percent with percentage points (10% to 15% is 5 points but a 50% rise).
4. Stacking discounts additively instead of sequentially.

Best Practices

• Decide the question type first — of, is-what-%, or change.
• Convert to decimals for clean multiplication.
• Sanity-check the answer — a discount is smaller than the price.
• Use a calculator to verify important figures.

Frequently Asked Questions

How do I calculate a percentage of a number?

Divide the percentage by 100 and multiply by the number. For 20% of 250: (20 / 100) x 250 = 50.

How do I find what percentage one number is of another?

Divide the first number by the second and multiply by 100. For 30 out of 120: (30 / 120) x 100 = 25%.

How do I convert a percentage to a decimal?

Divide the percentage by 100. So 45% becomes 0.45, which you can then multiply by any amount.

What is the difference between percent and percentage points?

Moving from 10% to 15% is a rise of 5 percentage points but a 50% relative increase. Percentage points measure the absolute gap; percent measures the relative change.

What is the easiest way to calculate percentages?

Use an online percentage calculator: enter the numbers and it applies the correct formula instantly without manual decimal conversion.

Conclusion

Percentages stop being intimidating once you know there are only a few questions to ask. Multiply by the decimal to find a percentage of a number; divide and multiply by 100 to express a ratio. Match the situation to the formula — and use the free calculator whenever speed and accuracy matter.

👉 Calculate any percentage now →

Related Resources

• Percentage Calculator: Complete Guide — the full how-to
• Percentage Increase Formula — calculate growth
• Percentage Decrease Formula — calculate drops
• Profit Percentage Formula — margin and markup