Choosing vending machine slots is a revenue decision, a labor decision, and a route decision at the same time. Every slot has limited capacity, so giving it to one product means giving up the sales and contribution another product could produce. The goal is not to make every machine look full. It is to use the available slots in a way that keeps products available, customers interested, and each stop worth serving.
Start with units sold and contribution per slot
Rank products by units sold over a consistent period, then add gross margin and contribution per slot to the view. Units sold shows velocity: a fast seller earns its space repeatedly and gives you a clearer restock signal. Gross margin shows what remains after product cost. Contribution per slot combines those ideas by asking how much gross profit a slot produces over a week or month. A high-margin item is not automatically the best choice if it sells slowly and blocks a dependable seller. Keep staples that move, then reserve measured space for higher-margin or test products that fit the venue.
Respect capacity, stock-outs, and spoilage
A slot mix only works when the machine can hold enough of each product between visits. Compare average daily units with slot capacity and your actual restock cadence. If a product sells out before the next visit, it may need another facing or a larger capacity format. If it regularly expires, its margin on paper is irrelevant to the route. Track stock-outs, spoilage, and the number of extra cases carried or discarded. Restock labor matters too: a complicated mix can add picking and loading time without adding enough contribution to justify the work. The best mix is one your team can replenish accurately on the schedule the route can support.
Match the mix to venue traffic and dayparts
Product demand changes with the venue and the hour. An office may favor coffee, water, and compact snacks during morning and afternoon breaks. A factory or distribution center may create stronger demand for filling food and energy drinks around shift changes. A hotel lobby, hospital, or transit location can have a broader daypart pattern and more visitors who make an impulse purchase. Review sales by day of week and, when available, time of day. Use that evidence to shift slots gradually instead of treating every machine as if it serves the same customer. Location-specific demand is usually more useful than a generic category plan.
Put slot results inside route economics
Slot-level performance should feed a route-level contribution view. Start with sales, subtract product cost, venue share, and payment fees, then subtract the labor and travel required to restock and maintain the stop. A machine with strong sales can still weaken route profitability if it requires a long drive, difficult parking, frequent emergency visits, or unusually slow loading. Compare contribution per stop and contribution per route hour, not only revenue per machine. This framing keeps a good-looking slot from hiding a poor operating pattern.
Test, measure, and rebalance
Make one controlled change at a time: give a proven seller one more facing, replace a slow SKU, or trial a venue-specific product in one slot. Record units sold, gross margin, stock-outs, spoilage, restock time, and route time before and after the change. Review after a normal demand window that includes the venue's busy and quiet periods. Keep changes that improve contribution without creating extra work, and reverse changes that only move sales around. A short measurement and review loop turns slot allocation into an operating habit: check the results on each route review, rebalance the mix, and update the next restock plan from what the machine actually sold.