Percentage Change Calculator
Calculate the percentage increase or decrease between any two values with the formula shown.
Find percent change for prices, scores, population, and revenue.
Percentage change measures how much a value has increased or decreased relative to its starting point. It is one of the most widely used calculations in finance, science, economics, and everyday life.
Percentage Change formula:
Percentage Change = ((New Value − Old Value) / |Old Value|) × 100
Percentage Increase:
Increase % = ((New − Old) / Old) × 100 (positive result)
Percentage Decrease:
Decrease % = ((Old − New) / Old) × 100 (positive result; or use the same formula and get a negative)
Reverse calculation (finding original value):
Original = New Value / (1 + Change%/100)
What each variable means:
- Old Value (Original) — the starting or reference point; this is always the denominator
- New Value — the ending or current value
- |Old Value| — absolute value; used when the original could be negative (e.g., negative earnings turning positive)
Worked examples:
Example 1 — Price increase: A product goes from $40 to $52. Change = (($52 − $40) / $40) × 100 = ($12 / $40) × 100 = +30% increase
Example 2 — Price decrease (sale): Regular price $120, sale price $90. Change = (($90 − $120) / $120) × 100 = (−$30 / $120) × 100 = −25% decrease
Example 3 — Find original price after a 15% increase: Current price is $115. What was it before? Original = $115 / 1.15 = $100
Example 4 — Negative base (company losses): Net income went from −$200K to −$50K. Change = ((−50K − (−200K)) / |−200K|) × 100 = ($150K / $200K) × 100 = +75% improvement
Common mistake: Confusing “25% off” with “75% of the price” — they are the same thing but expressed differently. Also, a 50% loss followed by a 50% gain does NOT return to the original value: $100 → $50 → $75 (net −25%).