How to Calculate Percentage Change (Increase & Decrease)

The Percentage Change Formula

Percentage change measures how much a value has increased or decreased relative to its original value. One formula covers both increases and decreases:

Percentage Change = ((New Value − Old Value) ÷ Old Value) × 100

If the result is positive, the value increased. If it is negative, the value decreased.

Worked Examples

Example 1 — Price increase: A product cost $40 and now costs $52. Percentage change = ((52 − 40) ÷ 40) × 100 = (12 ÷ 40) × 100 = +30%. The price increased by 30%.

Example 2 — Salary change: Your salary was $58,000 and was increased to $63,000. Percentage change = ((63,000 − 58,000) ÷ 58,000) × 100 = (5,000 ÷ 58,000) × 100 = +8.62%.

Example 3 — Population decrease: A town had 12,400 residents and now has 10,850. Percentage change = ((10,850 − 12,400) ÷ 12,400) × 100 = (−1,550 ÷ 12,400) × 100 = −12.5%. The population declined by 12.5%.

Common Mistakes

One of the most frequent errors is using the wrong base number — dividing by the new value instead of the old value. The old value is always the denominator. The formula measures change relative to where you started, not where you ended up.

A second common mistake is confusing percentage change with percentage points. If an interest rate goes from 2% to 5%, that is a change of 3 percentage points — but a percentage change of 150%. These describe different things and should not be used interchangeably.

A third error: forgetting the sign. A negative result means a decrease. Always check whether the result should be an increase or decrease to catch arithmetic errors.

Real-World Uses

Percentage change comes up in virtually every domain that involves comparing numbers over time:

• Finance: Investment returns, stock price movements, revenue growth, cost changes
• Statistics and research: Population changes, survey result shifts, scientific measurement comparisons
• Everyday shopping: Sale discount calculations, price comparisons between stores or periods
• Sports and fitness: Performance improvements, weight change tracking, season-over-season statistics
• Business: Year-over-year sales, customer count changes, market share shifts

Percentage Change vs Percentage Increase

Percentage change is the general formula — it works for both increases and decreases. Percentage increase specifically describes situations where the new value is higher than the old value. The formula is identical; the distinction is just about direction.

When you only want to calculate how much larger a new value is compared to the old, you can use percentage increase. When you want a single formula that handles both directions, use percentage change.

Calculate Percentage Change

Use our free Percentage Change Calculator to enter any two values and see the exact percentage change instantly. For increase-only calculations, the Percentage Increase Calculator is also available.