Percentage Change Calculator Formula

Understand the math behind the percentage change calculator. Each variable explained with a worked example.

Use the Percentage Change Calculator

Formulas Used

Percentage Change (%)

pct_change = ((new_val - old_val) / abs(old_val)) * 100

Absolute Change

absolute_change = new_val - old_val

New / Old Ratio

ratio = new_val / old_val

Variables

VariableDescriptionDefault
old_valOld Value80
new_valNew Value100

How It Works

How to Calculate Percentage Change

Formula

% Change = [(New - Old) / |Old|] * 100

Percentage change measures the relative difference between two values. A positive result indicates an increase; negative indicates a decrease. Using the absolute value of the old value in the denominator handles cases where the old value is negative.

Worked Example

A price changes from $80 to $100.

old_val = 80new_val = 100
  1. 01Change = 100 - 80 = 20
  2. 02% Change = (20 / 80) * 100 = 25%
  3. 03Ratio = 100 / 80 = 1.25
  4. 04The price increased by 25%

Ready to run the numbers?

Open Percentage Change Calculator