How to Calculate Percentage Change (Increase and Decrease)

Percentage change describes how much a value moved, relative to where it started. The same $10 move means something very different depending on whether it started from $20 or $2,000, and percentage change is what makes those two situations comparable.

Percentage Change % = ((New Value − Old Value) / |Old Value|) × 100.

Step 1: Identify which value is old (the starting point) and which is new (the result) — this is the most common place to make an error. Step 2: Subtract the old value from the new value. Step 3: Divide by the absolute value of the old value, so a negative starting value doesn't flip the sign of the answer. Step 4: Multiply by 100.

A product priced at $40 rises to $50. New − Old = $50 − $40 = $10.

$10 / $40 × 100 = 25%. The price increased by 25%.

Monthly visits fall from 8,000 to 6,000. New − Old = 6,000 − 8,000 = −2,000.

−2,000 / 8,000 × 100 = −25%. The negative sign shows a decrease — traffic fell by 25%.

A conversion rate moving from 2% to 3% is a 1 percentage point increase, but it is a 50% percentage change (an increase of 1 out of a base of 2). Headlines and reports sometimes blur this distinction, and the two numbers can look similar while meaning very different things — always check which one is being reported.

Almost every wrong answer traces back to one of these.