Percentage Change Calculator
The signed percent change from one value to another, up or down.
The formula
change % = (new - old) / |old| × 100
From 240 to 276: (276 - 240) / 240 × 100 = +15%. Positive means growth, negative means decline, and the old value is always the base.
Change vs. difference
Percentage change is directional: it has a before and an after, and swapping them changes the answer. When neither value is the natural starting point (comparing two products, two labs, two cities), the symmetric percentage difference, measured against the average of the two, is the fairer figure.