Your grocery receipt is the percent-change battlefield of American life. When a gallon of milk climbs from $3.50 to $4.20, the percent change is (new − old) ÷ old × 100 — here ($4.20 − $3.50) ÷ $3.50 × 100, about a 20% jump. The formula always anchors to the starting value: subtract the old number from the new one, divide by the old number, and multiply by 100 to turn the decimal into a percent. A positive answer is growth; a negative answer is shrinkage.

Investors watch it on stock tickers, managers on quarterly revenue, and shoppers on sale tags. The classic trap is asymmetry: a stock that falls 50% needs a 100% gain to recover, because the second percent anchors to the smaller base. This calculator performs the heart of the computation. Type the raw difference (new − old) in the Variable A box — for the milk, 0.70 — and type 1 ÷ old in the Variable B box (1 ÷ 3.50 ≈ 0.2857), and the Result box shows 0.20. Multiply by 100 in your head to read the 20% change.

With the pre-filled defaults — Variable A 10, Variable B 5 — the Percent Change Calculator returns Result 50.0000. Change any input and those results update instantly, so you can see exactly how each number you enter moves the answer.