Excel beginner percentage change growth finance

Percentage Change Formula in Excel

Percentage Change Formula is a Excel function that percentage change = (new - old) / |old|. Formula Genius generates and validates this formula automatically from a plain-English prompt.

Calculate growth rates, month-over-month changes, and YoY comparisons. With proper handling for zero and negative baselines.

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The Formula

Prompt

"Calculate percentage change from old value to new value"

Excel 
=IFERROR((B2-A2)/ABS(A2),"")

Percentage change = (new - old) / |old|. Using ABS handles negative baselines correctly. IFERROR catches division by zero when the old value is 0.

Step-by-Step Breakdown

  1. B2 is the new value, A2 is the old value
  2. (B2-A2) calculates the absolute change
  3. ABS(A2) uses the absolute value of the baseline to handle negatives
  4. IFERROR returns blank when A2 is 0 (avoiding #DIV/0!)
  5. Format the cell as Percentage to display correctly

Edge Cases & Warnings

  • Old value of 0: percentage change is undefined — returns blank
  • Old value negative, new value positive: ABS ensures correct positive result
  • Both values 0: returns blank (0/0 is undefined)
  • Very small old values can produce misleadingly large percentages

Examples

Prompt

"Old=100, New=125"

Excel 
25% increase
Prompt

"Old=200, New=150"

Excel 
-25% decrease
Prompt

"Old=0, New=50"

Excel 
Blank (undefined)

Frequently Asked Questions

Why use ABS in the denominator?

Without ABS, going from -100 to -50 gives (-50-(-100))/-100 = -50%, which is wrong. Using ABS gives +50%, which correctly shows the value moved toward zero.

How do I calculate YoY growth?

Same formula, just compare the same month across years: =(Jan2026-Jan2025)/ABS(Jan2025). Format as percentage.

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