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FINPACK.CPIAVGCHANGE

FINPACK.CPIAVGCHANGE returns the percentage change between two consecutive average CPI periods of equal length.

Use this function when you want to smooth monthly CPI fluctuations and compare average CPI levels over consecutive periods.

Syntax​

=FINPACK.CPIAVGCHANGE(country, series, months, year, month)

Arguments​

ArgumentDescription
countryCountry code for the CPI data. For example, "ca" for Canada or "us" for the United States.
seriesCPI series identifier. For example, "all-items".
monthsNumber of months in each averaging period. Must be greater than 0.
yearEnding year of the current averaging period.
monthEnding month of the current averaging period, from 1 through 12.

Text arguments must be enclosed in quotation marks when entered directly in a formula.

How the calculation works​

Suppose you use:

=FINPACK.CPIAVGCHANGE("ca","all-items",12,2026,9)

The current 12-month period is:

October 2025 through September 2026

The immediately preceding 12-month period is:

October 2024 through September 2025

finPack calculates the average CPI for each period and compares those two averages.

Conceptually:

Current-period average CPI
────────────────────────── - 1
Prior-period average CPI

The result is rounded to one decimal percentage point.

Return value​

FINPACK.CPIAVGCHANGE returns a numeric ratio.

For example, a returned value of:

0.026

represents:

2.6%

Because the result remains numeric, it can be used directly in other Excel calculations.

Percentage formatting​

Apply a percentage number format to the Excel cell to display the result as a percentage.

For example:

0.026

displayed as a percentage with one decimal place becomes:

2.6%

Flexible period lengths​

The months argument controls the length of both averaging periods.

For example:

=FINPACK.CPIAVGCHANGE("ca","all-items",3,2026,9)

compares consecutive three-month average CPI periods.

=FINPACK.CPIAVGCHANGE("ca","all-items",6,2026,9)

compares consecutive six-month average CPI periods.

=FINPACK.CPIAVGCHANGE("ca","all-items",12,2026,9)

compares consecutive twelve-month average CPI periods.

Using cell references​

Arguments can also refer to worksheet cells.

For example, suppose:

CellValue
A2ca
B2all-items
C212
D22026
E29

You can use:

=FINPACK.CPIAVGCHANGE(A2,B2,C2,D2,E2)

This is useful when the averaging period or ending date needs to vary throughout an Excel model.

CPI Average Change versus CPI Increase​

FINPACK.CPIAVGCHANGE and FINPACK.CPIINCREASE answer different questions.

FINPACK.CPIINCREASE compares two individual monthly CPI observations:

September 2026
versus
September 2025

FINPACK.CPIAVGCHANGE compares two average CPI periods:

Average CPI: October 2025 through September 2026
versus
Average CPI: October 2024 through September 2025

Use FINPACK.CPIINCREASE for the conventional same-month annual CPI change.

Use FINPACK.CPIAVGCHANGE when you want to compare average CPI levels over consecutive periods.

Estimated observations​

Either averaging period may contain an observation that was not published by the provider but was estimated using the provider's recommended methodology.

FINPACK.CPIAVGCHANGE continues to return a numeric result when all observations required for the calculation are available.

The worksheet function itself does not append an estimated-data label to the cell result.

Use the CPI Average Change section of the finPack task pane when you need to see whether the calculation includes estimated observations.

Errors​

FINPACK.CPIAVGCHANGE returns an Excel error when the requested calculation cannot be completed.

For example, this can occur when:

  • The country is not supported.
  • The CPI series is unavailable.
  • months is less than 1.
  • The month is not between 1 and 12.
  • One or both averaging periods do not contain all required CPI observations.
  • The requested periods extend beyond the available CPI history.
  • The BPOpti service cannot provide the requested result.

Excel may display:

#N/A

Internet connection​

FINPACK.CPIAVGCHANGE performs the calculation through BPOpti services and therefore requires an internet connection when Excel calculates the function.

Use CPI Average Change when you want to select the averaging period interactively and see whether the result includes estimated CPI observations.