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Percentage Function in Excel - Calculate Growth, Discounts & Variance

Calculate percentage change, percentage difference, growth rates, and conversions with the Excel percentage function....

Quick Start

Syntax

=(Part/Total) or =(New-Old)/Old

Parameters

Part/Total - Required. Basic percentage: divide part by total (e.g., 25/100 = 25%). Format as percentage.

(New-Old)/Old - Optional. Percentage change: subtract old from new, divide by old. Shows growth or decline.

Simplest Example

ABC
1MonthSales% Change
2January45000
3February54000
4
=(B3-B2)/B2
20%

Quick Reference

Basic Percentage
=(Part/Total)*100

What percent is 25 out of 200?

=(25/200)*100 → 12.5%

Percentage Change
=(New-Old)/Old*100

From 50 to 75 = ?% increase

=(75-50)/50*100 → +50% increase

Percentage Difference
=ABS(A-B)/((A+B)/2)*100

Compare two values: 40 vs 60

=ABS(40-60)/50*100 → 40% difference

Increase by Percentage
=Original*(1+Percentage)

Increase 100 by 20%

=100*(1+20%) → 120

Real-World Examples

Calculate Monthly Sales Growth

Compare this month's sales to last month and calculate the percentage change to track business growth or decline. The percentage change formula in Excel is essential for sales managers, business analysts, and executives monitoring performance trends. This Excel percentage function reveals whether revenue is growing, stagnating, or declining - critical for forecasting, budgeting, and strategic planning. Track month-over-month growth rates, identify seasonal patterns, measure marketing campaign effectiveness, and communicate performance to stakeholders with clear percentage metrics that everyone understands using the percentage function.

ABC
1MonthSales% Change
2January$45,000
3February$54,000
=(B3-B2)/B2
+20.0%
4March$48,600-10.0%
Pro Tip: Format cells as Percentage (Ctrl+Shift+%) instead of multiplying by 100 - cleaner and easier to maintain.
Pattern: Percentage Change: (New - Old) / Old
Year-over-Year (YoY) Percentage Comparison

Compare performance across different years - essential for annual reports, investor presentations, and long-term trend analysis using the Excel percentage function. Year-over-year percentage change eliminates seasonal fluctuations and provides clear growth metrics. CFOs, financial analysts, and business strategists rely on YoY percentage calculations to assess sustainable growth, benchmark against competitors, and demonstrate company performance to investors and boards. This Excel percentage formula handles multi-year comparisons for revenue, expenses, customer counts, market share, and any metric that matters for business intelligence.

ABCD
1Metric20232024YoY Change
2Revenue$500K$625K
=(C2-B2)/B2
+25.0%
3Expenses$350K$385K+10.0%
Pattern: YoY Change: (Current Year - Prior Year) / Prior Year

Common Mistakes to Avoid

=(New-Old)*100Forgetting to divide by the Old value

❌ The Problem:

  • Calculates absolute difference, not percentage change
  • Results are wildly incorrect (e.g., 5000% instead of 50%)
  • Common beginner mistake in percentage calculations
  • Leads to wrong business decisions based on bad data

✅ Solution:

=(New-Old)/Old

Percentage change requires dividing by the original (Old) value. The Excel percentage function structure is: (difference) divided by (baseline). Without division, you get absolute change, not relative percentage change. Always divide by the starting value to get accurate percentage growth or decline using the percentage formula in Excel.

=(B3-B2)/B3Dividing by the wrong value (New instead of Old)

❌ The Problem:

  • Inverted percentage - calculates reverse relationship
  • Asymmetric growth/decline percentages (e.g., +100% up ≠ -100% down)
  • Confuses readers expecting standard percentage change
  • Makes trend analysis inconsistent and misleading

✅ Solution:

=(B3-B2)/B2

Always divide by the OLD value (baseline, starting point, earlier period). The percentage formula in Excel measures how much something changed relative to where it started. Dividing by the new value gives a different, non-standard metric that breaks comparability across periods.

=A1/B1 (displayed as 0.25 instead of 25%)Not formatting cells as percentage

❌ The Problem:

  • Decimal display (0.25) confuses readers expecting percentage (25%)
  • Requires mental conversion to understand the value
  • Inconsistent presentation in reports and dashboards
  • Looks unprofessional in client-facing materials

✅ Solution:

=A1/B1 formatted as Percentage

Use Excel's Percentage format (Ctrl+Shift+% or Home → Number → Percentage). The Excel percentage function itself calculates the decimal (0.25), but formatting displays it as 25%. This is cleaner than multiplying by 100, and the underlying decimal value works correctly in further calculations. For advanced rounding, combine with <Link href="/formulas/round">ROUND</Link>.

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