Rolling Averages: What They Are and How To Calculate Them

Updated June 24, 2022

Rolling average = sum of data over time / time period

Tracking a company's trends can help executives understand whether the business is successful. Rolling averages can give those executives the data they need to assess those trends. Understanding what a rolling average is and how to calculate one gives you the tools you need to figure out how your business changes over time. In this article, we define rolling averages, give you the formula for calculating it and offer a step-by-step guide on how to complete the formula to help you determine business trends over any period you choose.

What is a rolling average?

A rolling average, sometimes referred to as a moving average, is a metric that calculates trends over short periods of time using a set of data. Specifically, it helps calculate trends when they might otherwise be difficult to detect. For instance, if your data set includes many points where the numbers shift up and down drastically, you might not see whether it trends up or down over time.

To discover the trend, a rolling average uses smaller parts of the data. For instance, you might use the numbers collected over the last 30 days and find out their average. Then, the average rolls or moves for each new period. Making these calculations for every 30 day period allows professionals to discover the way the average changes as time moves forward.

Why are rolling averages useful?

Rolling averages are useful for finding long-term trends otherwise disguised by occasional fluctuations. For instance, if your company sells ice, you might notice a fluctuation upwards on hot days. If the temperature in your area fluctuates often, your data might become difficult to track. Calculating a rolling average can help you determine your ice sales trends for each period. While you might notice your ice sales go down in cooler months, your business might trend up over the entire year.

Rolling averages can also help you determine the factors that cause your trends. This can help you prepare and make decisions for the future of your business. If weather makes your ice sales fluctuate on hot days, you might notice an upward trend during the summer months. This can help you set strategic goals and determine how much ice to produce during those months based on previous data.

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How do you calculate a rolling average?

Professionals use a formula to calculate rolling averages. This involves collecting data over time and inserting it into the formula. The formula looks like this: rolling average = sum of data over time / time period. These steps help you figure out which numbers to include in the formula, then how to solve the equation:

1. Determine your time period

Figuring out the time period for your rolling average depends on your goal in calculating it. For instance, if you hope to determine how much each month's sales affect your trends, you might choose a rolling 12-month period. When you want to know which day of the week affects the trend, you could decide to average a rolling seven-day period.

2. Collect the data

Next, you need the data based on the time you chose. It's helpful to collect data over a longer period than you chose. For example, if you tracked how monthly sales trends over the year, you might collect data from the past 18 months or the past year. Having more data can help you determine the way trends change.

3. Add your earliest totals

To track your trends, it's helpful to start with the earliest totals you have available. If you have sales totals from July 2019 to December 2020, a good practice is to begin with the 12-month period from July 2019 to June 2020 and add them all together. For example, these might be your totals for those months:

July 2019: $48,904

August 2019: $49,615

September 2019: $47,546

October 2019: $51,600

December 2019: $50,455

January 2020: $50, 690

February 2020: $51,900

March 2020: $52,420

April 2020: $51,981

May 2020: $53,315

June 2020: $54,100

Total: $526,526

4. Divide the total by your time period

Dividing the total by your time period gives you your average for each unit. If you're calculating your average for a 30-day period, divide by 30. If you're calculative over a 12-month period, divide by 12. To continue our example, for your total of $526,526 over 12 months, it might look like this:

$526,526 / 12 = $46,877.17

This means your business averaged $46,877.17 per month from July 2019 to June 2020.

5. Calculate the average for your next rolling period

Calculating your next rolling period involves leaving off your earliest unit and adding in your next unit. In the monthly example, this means leaving off the sales from July 2019 and adding in your sales from July 2020. This helps you calculate your average for the 12-month period from August 2019 to July 2020. If your sales total $55,000 in June 2020, your new total would be $532,622. Again, since it's a 12-month period, dividing by 12 can give you your monthly average.

$532,622 / 12 = $44,385.17

6. Continue the formula for each rolling period

As you continue, the rolling period keeps moving. As you continue, removing the earliest month's sales and adding in the next and completing the formula gives you each 12-month period's average. Your next 3 month's sales might look like this:

August 2020: $54,200

September 2020: $55,600

October 2020: $56,100

This helps you continue to calculate your rolling period averages. When placing them into the formula, your averages look like this:

September 2019 to August 2020: $537,207 / 12 = $44,767.25

October 2019 to September 2020: $545,261 / 12 = $45,438.42

November 2019 to October 2020: $549,761 / 12 = $45,813

With these calculations, you can determine that for each rolling period, your sales typically trend upward.

7. Complete the formula regularly

As you continue to run your business, you can continue to complete the formula as you collect new data. This way, you can regularly determine your rolling average so you can continue to track your trends. Then, you can better understand the health of your business, report it to executives and shareholders and make decisions that prepare you for the future of your company.