Compare Average CPI Periods

This example compares the average Canadian All-Items CPI over two consecutive 12-month periods.

This type of comparison can help smooth month-to-month fluctuations by comparing average CPI levels rather than individual monthly observations.

Example

We want to calculate:

Input	Value
Country	Canada
CPI Series	All-Items
Period length	12 months
Ending year	2026
Ending month	September

The current period is:

October 2025 through September 2026

The preceding period is:

October 2024 through September 2025

How the calculation works

finPack first calculates the average CPI for each period.

Conceptually:

Current average
= Average CPI from October 2025 through September 2026

Prior average
= Average CPI from October 2024 through September 2025

finPack then calculates:

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

The result is rounded to one decimal percentage point.

Method 1: Use the finPack task pane

At the top of the task pane:

1. Select Canada.
2. Select All-Items.

In the CPI Average Change section:

1. Enter 12 as the period length.
2. Enter 2026 as the ending year.
3. Select September as the ending month.
4. Select Calculate CPI Average Change.

finPack displays:

Period    12 months
Ending    2026-09
Increase  2.6%

If one or more CPI observations used in the calculation are estimated, finPack adds:

(includes estimated)

to the result.

Method 2: Use FINPACK.CPIAVGCHANGE

The same calculation can be performed directly in an Excel cell.

Enter:

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

The function returns a numeric ratio.

For example, a displayed result of:

2.6%

is returned to Excel as:

0.026

Format the cell as a percentage with one decimal place to display the result as:

2.6%

Use cell references

Suppose the worksheet contains:

Cell	Value
A2	ca
B2	all-items
C2	12
D2	2026
E2	9

Enter:

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

You can now change the period length, ending year, or ending month without rewriting the formula.

Try a shorter period

CPI Average Change is not limited to annual periods.

For example:

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

compares:

Average CPI: July 2026 through September 2026

with:

Average CPI: April 2026 through June 2026

Similarly:

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

compares consecutive six-month average CPI periods.

CPI Average Change versus CPI Increase

These calculations answer different questions.

CPI Increase

FINPACK.CPIINCREASE compares two individual monthly CPI values:

September 2026
versus
September 2025

CPI Average Change

FINPACK.CPIAVGCHANGE compares average CPI over two consecutive periods:

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

Use CPI Increase when you need the conventional same-month 12-month change.

Use CPI Average Change when comparing average CPI levels over consecutive periods better suits the analysis.

Estimated observations

If either averaging period contains an observation that was not published by the provider but was estimated using the provider's recommended methodology, the task pane identifies the result as includes estimated.

The worksheet function continues to return a numeric result.

Related topics

• FINPACK.CPI — Retrieve the individual CPI values used in a comparison.
• FINPACK.CPIINCREASE — Complete function reference.
• FINPACK.CPIAVGCHANGE — Complete function reference.
• CPI Value — Detailed instructions for the task-pane feature.
• Calculate Annual CPI Increase — Compare the selected month with the same month one year earlier.
• Estimated CPI Observations — How finPack identifies estimated CPI data.
• CPI Data — Review the latest CPI Increase in the task pane.
• Compare Average CPI Periods — Compare consecutive average CPI periods instead of individual monthly observations.