Percentage Change Calculator 2026

Frequently Asked Questions

• What is the percentage change formula? +
  (New Value − Original Value) ÷ Original Value × 100. If the result is positive, the value increased; if negative, it decreased. Always divide by the absolute value of the original number to keep the direction (sign) meaningful even when the original was negative.
• Why does a 20% increase then a 20% decrease not return the original number? +
  Because each percentage is calculated against a different base value. $100 increased 20% is $120. $120 decreased 20% is $96, not $100 — the second calculation used the larger $120 as its base. This is one of the most common percentage mistakes in business.
• What's the difference between percentage change and percentage points? +
  Percentage change is relative (a margin moving from 20% to 25% is a 25% relative increase). Percentage points is absolute (the same move is described as +5 percentage points). Mixing these up is a frequent source of confusion in financial reporting.
• Can percentage change be used for margin comparisons? +
  Yes, but be careful with the label. If your margin moves from 20% to 25%, that's a 5 percentage-point increase, but a 25% percentage change in the margin figure itself. Use this calculator to get the percentage change number, then state clearly whether you mean points or percent.
• What if my original value is zero? +
  Percentage change is undefined when the original value is zero — you can't calculate a percentage change from nothing, since any positive number technically represents an infinite increase. In that case, report the absolute change in dollars instead.

Common Percentage Change Mistakes

• Averaging percentage changes incorrectly. A 10% gain followed by a 10% loss does not average to 0% — it's actually a small net loss, because the second percentage applies to a different (larger, then smaller) base.
• Confusing percentage change with percentage points. "Sales are up 10%" and "market share is up 10 points" describe completely different magnitudes of change — mixing these terms in a report can misstate results by an order of magnitude.
• Forgetting the sign matters in comparisons. A −15% change and a +15% change are opposite directions with the same magnitude — always check the sign before reporting a trend as positive or negative.

Percentage Change in Financial Reporting

Year-over-year (YoY) and month-over-month (MoM) percentage change figures are standard in almost every financial report, from small business dashboards to public company earnings calls. The key discipline is consistency: always compare the same time period length (a 31-day month against another 31-day month, not against February), and always state clearly which direction the comparison runs — "up 12% from last year" and "last year was 12% lower" describe the same fact but can read very differently in a summary.