What if the original value is zero?

Percentage change from zero is undefined because you cannot divide by zero.

Percentage Change Calculator

Measure how much a value grew or shrank from A to B. Positive results are increases; negative results are decreases.

Understanding percentage change

Percentage change compares two values: how much something grew or shrank relative to where it started. It is the language of growth rates, not of “add X% to this number.”

Good for

Year-over-year or month-over-month growth
Price or metric moves when you know both endpoints
Checking whether a jump sounds large in relative terms

Try the calculator

Percentage Change

Calculate the percent change from A to B

From (original value)

To (new value)

Result

Enter values to calculate

Measure how much a value grew or shrank from A to B. Positive results are increases; negative results are decreases. Read related guides.

The comparison formula

Change % = ((new − original) ÷ |original|) × 100. From 80 to 100: 20/80 × 100 = 25% increase. From 100 to 80: −20/100 × 100 = −20% (a 20% decrease).

Notice asymmetry: going up 25% and then down 20% can return to the start, because the bases differ. Always state the direction and the starting point.

Percentage points vs percent change

If a rate moves from 10% to 12%, that is +2 percentage points, but a 20% relative increase. Journalists and analysts mix these constantly. Use this calculator for relative change between raw numbers; read our guide when the numbers themselves are already percents.

Zero and missing data

You cannot compute a meaningful percent change from an original value of zero with the standard formula. Likewise, define which snapshot is “original” in time series so you do not accidentally reverse the comparison.

Worked examples

Example calculations for Percentage Change
Question	Answer
From 80 to 100	25% increase
From 50 to 40	20% decrease
From 200 to 250	25% increase

Formula reference

Goal	Formula
% change A → B	((B − A) ÷ \|A\|) × 100

FAQ — Percentage Change

How is percentage change calculated?: ((new − original) ÷ |original|) × 100. From 80 to 100: (20 ÷ 80) × 100 = 25% increase.
What if the original value is zero?: Percentage change from zero is undefined because you cannot divide by zero.

Educational tool only — not tax, legal, or financial advice. Contact us with corrections.

Free calculators for every common percentage problem.