A Vending Product Has No Sales on Some Days: Include the Zero Days in Your Average
Leaving zero-sales days out of a vending average can make a slow-selling product look busier than it is. Decide which days belong in the comparison and include genuine zeros for those days. At the same time, keep missing data and periods when the product was unavailable separate, because they do not mean the same thing as no purchases.
Start with the question the average should answer. You might want average units per open day for replenishment planning, or average units per calendar day for a broader report. Either can be useful when labelled correctly. Problems arise when the denominator changes silently or only the days containing a sale are included.
Work through a small example
Suppose a hypothetical product sells two, zero, three, zero and zero units across five comparable open days. The total is five units, so the average is one unit per open day. Dividing only by the two days with sales gives 2.5, which answers a different question: the average on days when a sale occurred.
Neither calculation should be presented without its meaning. For planning the ordinary open-day requirement, the first figure includes the quiet days that the operator will encounter. The second may be useful for a specific analysis, but calling it the general daily average would conceal three days with no purchases and exaggerate the apparent pace of sales.
Distinguish zero from missing
Check whether a blank entry means no sales, a missing report or a product that was not listed. Do not replace every blank with zero automatically. Confirm the reporting convention with the system or operator and preserve uncertainty where the evidence is incomplete. A missing day should be labelled as missing until it can be resolved.
Likewise, note stockouts and access restrictions. A zero while the selection was empty does not demonstrate that customers did not want the product. You may need separate measures for observed sales and sales while available. Explain the limitation rather than using an adjusted figure to imply a level of demand that was never directly measured.
Keep the time basis consistent
Use the same date boundaries and comparable opening pattern when comparing products or periods. If one week includes a closure, show how it is treated. Avoid mixing a five-day office week with a seven-day site without explaining the denominator. Check that the product identity and saleable pack size are consistent across the records too.
For a vending business plan, retain both the total units and the number of relevant days beside the average. That makes the result reproducible and helps a colleague judge whether the observation period is sufficient. A single average without its total and period can hide more than it explains.
Use the result cautiously for replenishment
An average is a summary, not a promise that one unit will sell every day. Look at the pattern as well as the arithmetic. Purchases may cluster around particular shifts or activities. Use the site’s actual operating context and stock information when deciding quantities, rather than multiplying an unqualified average into a confident long-term forecast.
When the product or site arrangement changes, begin a clearly labelled new comparison rather than quietly mixing unlike periods. Keep previous results available with their assumptions. Including genuine zero days is a simple reporting improvement, but its value depends on accurate availability records, a stated denominator and a realistic understanding of what the observed sales can support.
Related guidance: A Vending Report Is Missing Several Days: Check the Data Gap Before Judging Sales.
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