To calculate year-over-year percentage change, subtract the previous year's value from the current year's value, divide by the previous year's value, and multiply by 100. A positive result represents annual growth, while a negative result represents an annual decline.
Enter an original value and a new value to calculate the percentage change, numerical difference, direction, and multiplier.
The earlier year's value provides the reference for measuring annual growth or decline.
Year-over-Year Percentage Change Formula
Year-over-year change compares a current period with the corresponding period one year earlier.
The previous year's value is the denominator because it is the starting reference.
Enter the previous and current values into the Percentage Change Calculator to calculate the annual change.
How to Calculate Year-over-Year Change
Use comparable values covering the same measurement period.
- Identify the previous year's value.
- Subtract it from the current year's value.
- Divide the difference by the previous year's value.
- Multiply by 100 and interpret the direction.
Worked Revenue Example
Suppose annual revenue rises from $200,000 to $250,000.
The numerical increase is $50,000.
Dividing 50,000 by 200,000 and multiplying by 100 gives year-over-year growth of 25 percent.
Year-over-Year Decline Example
Suppose revenue falls from $500,000 to $425,000.
The difference is minus $75,000.
Dividing minus 75,000 by 500,000 gives minus 15 percent, representing a 15 percent annual decline.
Website Traffic Example
Suppose annual website visits rise from 120,000 to 150,000.
The increase is 30,000 visits.
Dividing 30,000 by 120,000 and multiplying by 100 gives 25 percent year-over-year traffic growth.
Population Example
Suppose a population rises from 80,000 to 82,400.
The increase is 2,400 people.
Dividing 2,400 by 80,000 gives annual population growth of three percent.
Year-over-Year vs Month-over-Month
Year-over-year change compares a period with the same period one year earlier.
Month-over-month change compares one month with the immediately preceding month.
Year-over-year comparisons can reduce the effect of seasonal differences.
| Comparison | Earlier period | Later period |
|---|---|---|
| Year over year | June last year | June this year |
| Month over month | May this year | June this year |
| Quarter over quarter | Previous quarter | Current quarter |
Why Comparable Periods Matter
The two values should cover equivalent periods and use the same measurement rules.
Comparing a full year with only nine months can create a misleading result.
Changes in tracking methods, currency, reporting boundaries, or definitions should also be disclosed.
Year-over-Year Change and Seasonality
Many businesses experience predictable seasonal patterns.
Comparing December with November may reflect normal holiday activity rather than lasting growth.
Comparing December with the previous December often provides a more meaningful annual comparison.
Nominal vs Real Growth
Nominal growth uses the reported monetary values.
Real growth adjusts for price changes such as inflation.
Revenue can rise in nominal terms while its purchasing-power growth is smaller.
Common Mistakes
Do not divide by the current year's value.
Do not compare periods of different lengths without explaining the difference.
Do not describe a one-year change as a long-term growth rate.
Conclusion
Subtract the previous year's value from the current year's value, divide by the previous value, and multiply by 100.
Use equivalent annual periods and consistent measurement rules.
Use the Percentage Change Calculator to calculate annual growth or decline.
FAQs
What is the year-over-year growth formula?
Subtract the previous year's value from the current value, divide by the previous value, and multiply by 100.
Which year is the denominator?
Use the previous or earlier year's value.
What does negative year-over-year growth mean?
It means the current value is lower than the corresponding previous-year value.
Why use year-over-year instead of month-over-month?
It can reduce distortion from normal seasonal changes.
Can I compare periods of different lengths?
The comparison may be misleading unless the values are adjusted or the difference is clearly explained.