Average Monthly Sales Formula & How to Use It

This calculator works out your average monthly sales from the total sales over a given period and the number of months in that period. You enter the total sales amount and the time span, and you get the monthly average, plus the average per day if you need it. The formula is simple: divide total sales by the number of months.

Formula

The average monthly sales formula is:

Average Monthly Sales = Total Sales ÷ Number of Months

In symbols: A = S / N

• A = average monthly sales (currency per month)
• S = total sales over the period (currency)
• N = number of months in that period (months)

For example, if a business sold $120,000 over 12 months, the average is $10,000 per month.

Worked Example

Using the default values from the calculator above:

1. Total sales (S) = $120,000
2. Number of months (N) = 12
3. Apply the formula: A = 120,000 ÷ 12
4. Result: A = $10,000 per month

The calculator also shows the average per day assuming a 30-day month: $10,000 ÷ 30 = $333.33 per day.

When to Use This Formula

Use the average monthly sales formula whenever you need a quick, simple measure of typical monthly revenue over a period. It is commonly used for:

• Comparing performance across different time spans (e.g., a 6-month period vs. a 12-month period).
• Creating budgets or forecasts based on historical averages.
• Evaluating whether a business meets its monthly targets.
• Reporting to stakeholders who want a single number to gauge overall sales pace.

The formula is most useful when sales are relatively stable. If sales vary wildly from month to month, the average still gives a central tendency, but you should also look at the range or standard deviation to understand the variability.

How to Read the Result

The result is a simple arithmetic mean. A monthly average of $10,000 means that if you evenly spread the total sales across the months, each month would have $10,000. It does not mean every month actually had that amount—some months could be higher, some lower.

When comparing averages, always use the same time unit. For instance, compare a 12-month average to another 12-month average, not to a 3-month average, unless you adjust for the different lengths.

Common Mistakes and Misconceptions

• Using calendar months vs. 30-day months: The formula uses the number of months, not days. If you have daily sales data, you might want to compute the average per day first and then multiply by 30 (or 30.44 for an average month) to get a monthly figure. The calculator’s per-day output uses a 30-day month, which is a common approximation. For exact calendar months, use the actual number of days in each month.
• Including partial months: If your period includes a partial month (e.g., from January 15 to March 15), you must decide how to count it. One approach is to count it as 2 months, another is to count the exact number of days and divide by 30.44. The formula assumes whole months.
• Rounding too early: When doing the calculation by hand, keep extra decimal places until the final step. Rounding the total sales or the number of months before dividing can skew the result.
• Confusing average with median: The average can be pulled up by a few high-sales months. The median (the middle value when all months are sorted) is a better measure of “typical” if you have outliers. For example, if one month had a massive promotional spike, the average will be higher than most months actually achieved.

Limitations of the Formula

This formula is a simple arithmetic mean and does not account for trends, seasonality, or growth. If sales are increasing over time, the average will be lower than the most recent months and higher than the earliest months. A moving average or a linear trend line can give a better picture of the direction.

Also, the formula only works with numerical sales data. It does not consider the number of business days in a month, which can affect sales for businesses that close on weekends or holidays. For such cases, a daily average (total sales ÷ number of business days) might be more informative.

Finally, the result is only as good as the data. If the total sales figure includes returns, refunds, or taxes, decide whether those should be included. Typically, “net sales” (after returns and allowances) is used for a true average, but the formula works with any consistent definition.

Frequently Asked Questions

How do I calculate average monthly sales in Excel?

If you have monthly sales in cells A1 through A12, use the formula =AVERAGE(A1:A12). If you have daily sales and want a monthly average, first sum the daily sales for each month (e.g., with SUMIFS) and then average those monthly totals.

What if I only have annual sales?

Divide the annual total by 12 to get a rough monthly average. For a more accurate figure, consider the number of business days or seasonal patterns, but the simple division is the standard starting point.

Is the average monthly sales the same as the monthly recurring revenue?

No. Monthly recurring revenue (MRR) is a metric used by subscription businesses to measure predictable revenue from active subscriptions. Average monthly sales is a broader measure that includes one-time sales, services, and any other revenue.

Should I include sales tax in the total?

Usually, sales tax is not considered part of your sales revenue because it is collected on behalf of the government. Use net sales (before tax) for a true picture of your business’s revenue. If you include tax, the average will be inflated and not comparable to other periods that may have different tax rates.

How do I handle a period that is not a whole number of months?

Convert the period to days and divide by the average number of days in a month, which is 30.44 (365/12). For example, 45 days is approximately 1.48 months. Then divide total sales by 1.48 to get the monthly average.

Can I use this formula for forecasting?

Yes, but with caution. The average is a baseline. If you expect future months to be similar to the past, the average is a reasonable forecast. If you expect growth or seasonal changes, adjust the average accordingly or use a trend-based forecast.

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in t | Total sales | currency | 120000 | 0
in m | Number of months | months | 12 | 1
out avg | Average monthly sales | currency/month | t / m | 2
out perday | Average per day (30-day month) | currency/day | t / (m * 30) | 2