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How to Calculate Percentages in Excel (Complete Guide with Examples)

Understanding how to calculate percentages in Excel is essential for analyzing data effectively. Whether you’re working on sales reports, financial summaries, or school grades, Excel makes it easy to calculate and format percentages. In this article, we’ll walk you through several ways to calculate percentages in Excel, from simple formulas to practical examples you can use in real business scenarios.

✅ What Is a Percentage in Excel?

A percentage represents a ratio or a fraction of 100. In Excel, a percentage is simply a decimal formatted to display as a percent. For example:

• 0.75 becomes 75%
• 0.25 becomes 25%

You can apply the percentage format by selecting the cell, right-clicking, and choosing Format Cells > Percentage or by clicking the Percent Style (%) button on the ribbon.

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✅ Basic Percentage Formula

The most basic formula to calculate percentage is:

=Part / Total

Then, format the result as a percentage. For example:

If A2 = 50 and B2 = 200, use:

=A2 / B2

The result is 0.25, and formatting the cell as a percentage will display 25%.

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✅ How to Increase or Decrease by a Percentage

If you want to increase a number by a certain percentage, use:

=Original * (1 + Percentage)

To decrease by a percentage:

=Original * (1 - Percentage)

Example:

If A2 = 100 and you want to increase it by 15%:

=A2 * (1 + 15%)

→ Result: 115

To decrease it by 15%:

=A2 * (1 - 15%)`

→ Result: 85

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✅ How to Calculate the Percentage Change

To find how much something has increased or decreased compared to the original, use the formula:

=(New - Old) / Old

For example:

• Old value (A2): 80
• New value (B2): 100

Use:

=(B2 - A2) / A2

→ Result: 0.25, which becomes 25% after formatting.

This is particularly useful for tracking growth in revenue, website traffic, or stock prices.

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✅ Calculate What Percentage One Number Is of Another

If you want to find out what percentage one number is of another, use:

=Number / Total

Example:

• A2 = 30
• B2 = 200

Use:

=A2 / B2

→ 0.15 or 15%

This formula is useful for market share, composition ratios, or contribution analysis.

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✅ Find a Number Based on a Percentage

You can reverse the operation and find the actual number from a given percentage.

Formula:

=Percentage * Total

Example:

• You want to find what is 20% of 150:

=20% * 150

→ Result: 30

You can also use:

=0.2 * 150

Same result: 30

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✅ Real-Life Example: Sales Tax Calculation

Let’s say you have a product that costs $120 and a sales tax rate of 8%.

To calculate the tax amount:

=120 * 8%

→ Result: $9.60

To calculate the total price including tax:

=120 * (1 + 8%)

→ Result: $129.60

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✅ Using Percentage Format Correctly

When you type 15% into a cell, Excel treats it as 0.15.

But if you type 15 and format it as a percentage, Excel will convert it to 1500%.

✅ Always use actual decimal values (like 0.15) or type 15% directly.

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✅ Common Mistakes and How to Avoid Them

❌ Mistake 1: Dividing in the Wrong Order

Using Total / Part instead of Part / Total will give you the reciprocal.

✅ Always make sure you divide the smaller number by the larger one when finding percentages.

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❌ Mistake 2: Not Formatting as Percentage

If your formula returns a decimal like 0.4 and you forget to format the cell, you might misunderstand the result.

✅ Click the % button or press Ctrl + Shift + % to apply percentage formatting.

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✅ Bonus Tip: Conditional Formatting with Percentages

Want to visually highlight percentage thresholds?

1. Select your data range (e.g., C2:C20).
2. Go to Home > Conditional Formatting > Data Bars or Color Scales.
3. Use conditional formatting to highlight:
   • Over 90% (e.g., green)
   • Below 50% (e.g., red)

This is great for performance dashboards, grade sheets, or KPI reports.

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■ Summary: Quick Reference Formulas

Task	Formula Example
Part of total as percentage	=Part / Total
Increase by a percentage	=Amount * (1 + Percentage)
Decrease by a percentage	=Amount * (1 - Percentage)
Percentage change	=(New - Old) / Old
Find number from percentage	=Percentage * Total

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■ Final Thoughts

Mastering percentage calculations in Excel will help you unlock powerful insights in your data. Whether you’re preparing financial reports, analyzing trends, or simply budgeting your expenses, knowing how to apply percentage formulas can save time and improve accuracy.

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