Percentage Change Calculator

Percentage change = (new − old) ÷ old × 100. A positive result is an increase, a negative one a decrease.

One formula, both directions

Percentage change measures how much a number moved relative to where it started, and it carries a sign so it works whether the value rose or fell. Subtract the original from the new, divide by the original, and multiply by 100: a positive answer is an increase, a negative one a decrease. That single signed figure is what makes it the right tool for comparisons and reporting — you don’t have to know in advance which way the number went, and a column of percentage changes reads consistently whether the entries are up or down.

The “divide by the original” step is the one that matters: the change is always measured against the earlier, reference value, not the later one. Revenue moving from $1.2m to $1.5m is a +25% change (300k ÷ 1.2m); falling back from $1.5m to $1.2m is −20% (−300k ÷ 1.5m). The same $300k gap is a different percentage each way, because the base differs — which is exactly why you must be clear about which value is the reference.

Worked examples: Revenue $1.2m → $1.5m: (1.5 − 1.2) ÷ 1.2 × 100 = +25% (an increase). Revenue $1.5m → $1.2m: (1.2 − 1.5) ÷ 1.5 × 100 = −20% (a decrease). A share price $42.50 → $51.30: +20.7%.

Percentage change vs increase vs difference

Three related terms get used loosely, and the distinction matters in analytics and finance. The absolute change (or difference) is simply new minus old, in the original units — useful when the scale is what counts. The percentage change is that difference relative to the original, expressed as a signed percentage — the comparable, scale-free measure. A percentage increase or decrease is just the percentage change with its direction named: an increase is a positive change, a decrease a negative one. This calculator gives all three at once — the signed percentage, the direction, and the absolute change — so the right framing is always to hand.

It also shows the multiplier, which is the cleanest way to chain or reverse changes: a +25% change is ×1.25, a −20% change is ×0.8. Notice those two undo each other (1.25 × 0.8 = 1.0) only because they are measured against different bases — the classic trap when a metric rises then falls by the “same” percentage.

Using it for YoY, KPIs and reporting

Period-over-period percentage change is the backbone of business reporting: revenue and profit year-over-year, active users month-over-month, conversion rates quarter-on-quarter. Expressing every metric as a signed percentage change puts them on a common footing, so a dashboard can compare a small line and a large one fairly — a 30% rise in a niche product and a 5% rise in the flagship are immediately legible side by side. It is also how growth rates, churn, and price moves are quoted, and how analysts spot turning points when a long-positive series first goes negative.

Two cautions worth keeping in mind. Percentage change is undefined when the starting value is zero — there is no meaningful percentage rise from nothing — so the calculator flags that case and points you to the absolute change instead. And a large percentage change off a tiny base can mislead: a jump from 2 to 6 is +200% but may be noise. Always read the percentage alongside the absolute figures it came from.