how to calculate percent growth

If you want to measure how much a number has increased over time, percent growth is one of the fastest and most useful calculations you can learn. It is used everywhere: business revenue, website traffic, salaries, population, investments, and even student test scores.

What is percent growth?

Percent growth tells you how much a value changed compared with where it started, expressed as a percentage. It answers this question:

"How large is the change relative to the original amount?"

If the result is positive, you have growth. If it is negative, you have a decline (sometimes called negative growth).

Percent growth formula

Step-by-step process

• Step 1: Subtract the old value from the new value to find the change.
• Step 2: Divide that change by the old value.
• Step 3: Multiply by 100 to convert to a percentage.

Simple examples

Example 1: Revenue increase

A business made $80,000 last year and $100,000 this year.

• Change = 100,000 − 80,000 = 20,000
• Change / Old = 20,000 / 80,000 = 0.25
• Percent growth = 0.25 × 100 = 25%

Example 2: Decline in users

A website had 50,000 monthly users, then dropped to 42,500.

• Change = 42,500 − 50,000 = −7,500
• Change / Old = −7,500 / 50,000 = −0.15
• Percent growth = −0.15 × 100 = −15%

Reference table

Scenario	Old Value	New Value	Percent Growth
Sales growth	200	260	+30%
Expense reduction	900	810	−10%
No change	1,500	1,500	0%

Common mistakes to avoid

• Using the new value in the denominator: always divide by the old value for percent growth.
• Forgetting to multiply by 100: if your answer is 0.18, that means 18%.
• Ignoring negative signs: a negative percentage means decline.
• Mixing units: compare values in the same unit (e.g., dollars to dollars, not dollars to thousands of dollars).

What if the starting value is zero?

If the old value is zero and the new value is not zero, percent growth is mathematically undefined because you cannot divide by zero. In practical reporting, people may describe this as "new growth from zero," but it is not a standard percent growth calculation.

Percent growth vs. percentage points

These are not the same:

• Percent growth: relative change between two raw values.
• Percentage points: absolute difference between two percentages (e.g., 12% to 15% is +3 percentage points, not 25 percentage points).

When to use CAGR instead

If you are measuring growth across multiple years and want an annual average growth rate, use CAGR (Compound Annual Growth Rate), not simple percent growth.

CAGR is common in long-term investing and business forecasting because it smooths out year-to-year volatility.

Quick mental math tips

• If the new value is 10% higher, multiply old value by 1.10.
• If the new value is 25% higher, multiply old value by 1.25.
• If the new value is 20% lower, multiply old value by 0.80.

Final takeaway

To calculate percent growth, compare the change to the original value, then convert to a percent. Once you understand this pattern, you can evaluate trends faster, make clearer decisions, and communicate results with confidence.