Calculadora de variação percentual

Percentage change measures how much a value has grown or shrunk relative to its starting point: percent change = (new value − old value) ÷ old value × 100. A positive result is an increase; a negative result is a decrease.

Percentage change is always relative to the old (starting) value, not the new one — that's why a 50% increase followed by a 50% decrease does not return you to the original number. Going from 100 to 150 is a 50% increase, but going back from 150 to 100 is only a 33.3% decrease.

Example: a price that rises from 100 to 120 has increased by 20 (the absolute change) and by 20% ((120 − 100) ÷ 100 × 100). A drop from 120 back to 100 would be a decrease of about 16.7%, not 20%.

Percent change always uses the old value as the denominator — a drop from 200 to 100 is −50%, but a rise from 100 to 200 is +100%.

Stock tickers and economic reports use the same formula; watch whether they report relative to yesterday's close or a year-ago baseline.

Worked example with defaults old=100, new=120: absolute change +20, percent change +20%. Reversing to old=120, new=100 gives −16.67%, not −20%.

Successive changes multiply, not add — +10% then −10% on 100 lands at 99, not 100, because −10% applies to 110 afterward. Compound growth uses (1 + r₁)(1 + r₂), not r₁ + r₂, on investments, sale prices, and stock index returns quoted in financial news headlines. Retail managers use the same compounding logic when stacking seasonal markdowns across two quarters.

Markup versus margin confuse percent math — 25% markup on cost is not 25% margin on price; margin = markup/(1+markup) when converting seller pricing strategies. 25% markup on cost differs from 25% margin on price — margin = markup÷(1+markup) when converting pricing spreadsheets. Distinguish markup from margin in your explanation when converting seller pricing spreadsheets.

Zero old value makes percent change undefined — price from free promo ($0) to $5 has infinite relative change; enter meaningful baselines when comparing percentage swings. Old value zero makes percent change undefined — free-to-$5 promos have no meaningful relative percent without a nonzero baseline. Note that percent change is undefined when the old value is zero, not infinite growth.