What is percentage change?

Percentage change always points back to a chosen original. That value is the denominator reference after you subtract. If you relabel which month is "original," the percentage changes too, even when the absolute gap between numbers stays the same.

Positive results mean the new value sits above the original on the number line. Negative results mean it sits below. A zero result (before rounding) means no net movement. Very large magnitudes usually mean the baseline was small, not that the physical world became unstable.

Compared with percentage difference, which sometimes averages two observations in the denominator, percentage change is directional storytelling: from A to B. For a deeper comparison, see percentage change vs percentage difference.

Let O be the original and N the new value. Compute the signed difference N − O, divide by the absolute value of O, then multiply by one hundred. The absolute value in the denominator keeps the sign information in the numerator when O is negative.

If O is zero, stop. Relative change versus zero is undefined because division by zero has no meaning. In that situation, report absolute change or pick a different baseline. The calculator on the home page shows N/A for the same reason.

1. Write the baseline you defend as the original.
2. Record the updated measurement as the new value.
3. Subtract original from new.
4. Divide by the absolute original.
5. Multiply by one hundred and add context words (increase or decrease).

Sanity check: doubling implies about +100% versus the original. Halving implies about −50%. If those quick checks disagree with your spreadsheet, revisit which cell is labeled original.

Original price 80, new price 92. The difference is 12, and 12 ÷ 80 = 0.15, so the headline is +15%. If you mistakenly used 92 as the baseline, you would understate the story for merchandising teams.

For more numeric variety, continue with percentage change examples after you try the same pair on the calculator.