Ask five people at a growing consumer brand how they decide when to reorder, and you will usually get five different answers. One buyer reorders when the shelf looks thin. Another waits for the monthly count. A third keeps a personal spreadsheet nobody else can read. The result is predictable: pallets of slow movers taking up warehouse space while the one SKU that actually sells hits a stockout the week a retailer places its biggest order.
Min-max inventory replaces that guesswork with two numbers per SKU: a minimum stock level that triggers a reorder, and a maximum level that caps how much you buy. When on-hand inventory falls to the min, you order enough to bring it back up to the max. That is the entire system.
The simplicity is the point, and also the catch. This guide covers how min-max inventory works, how to set both levels with real numbers, where the method performs well, and where it starts quietly costing you margin.
How Min-Max Inventory Works
Min-max inventory control assigns every SKU a floor and a ceiling. The floor, your minimum, is the stock level at which you place a replenishment order. The ceiling, your maximum, is the most stock you want on hand at any time. The order quantity is whatever it takes to get from wherever you are back up to the max.
Take a coffee roaster stocking 12-ounce bags of a core blend. The min is set at 400 units and the max at 1,200. When a warehouse count shows 380 bags, the system triggers an order for 820 units. If stock had dipped further, to 300, the order would be 900. The order point stays fixed; the order quantity flexes with how far below the min you have fallen by the time anyone acts.
That flexing quantity is what separates min-max from a plain reorder point system. A reorder point tells you when to buy. Min-max also tells you how much, and it caps the answer so an enthusiastic buyer cannot turn a routine replenishment into six months of excess stock. The cap matters as much as the trigger: overbuying ties up cash and warehouse space just as surely as underbuying loses sales.
Min-max also differs from par-level replenishment, its close cousin from foodservice and healthcare. A par system tops stock up to a single target on a fixed schedule, whether you need 10 units or 400. Min-max only orders when the floor is breached, which means fewer, larger orders and less administrative churn. For products with real supplier minimums and freight costs, that difference shows up directly in landed cost.
How to Set Your Min and Max Levels
The minimum has to cover demand during the time it takes a replenishment order to arrive, plus a buffer for surprises. The standard formula is average daily demand multiplied by lead time in days, plus safety stock . A SKU selling 50 units a day with a 14-day supplier lead time needs 700 units of lead-time demand. Add 150 units of safety stock to absorb a late shipment or a demand spike, and the min lands at 850.
The maximum is the min plus however much demand you want each order to cover. If you want to reorder roughly monthly and the SKU sells 1,500 units a month, a max around 2,350 keeps the cadence. In practice, the max also has to respect constraints the formula ignores: supplier minimum order quantities, case-pack sizes, pallet configurations, available warehouse space, shelf life, and how much cash you are willing to park in inventory.
Two rules keep the numbers honest. First, calculate from actual sales history, not from what the team remembers selling. Averages pulled from a trailing 90 days of order data beat gut feel every time. Second, set levels per location, not per company. A min that works for your main warehouse will strand stock at a 3PL that ships a fraction of the volume.
Treat the first pass as a draft, not a commitment. Run the calculated levels against the last six months of actual orders and ask two questions: how many times would this SKU have stocked out, and how much cash would have been sitting above the max? A 30-minute backtest catches bad assumptions before they cost you a container's worth of margin.
Where Min-Max Replenishment Works Well
Min-max earns its keep on items with steady, predictable demand. Core products that sell at a consistent weekly rate, packaging and shipping supplies, ingredients and components with stable usage, and the long tail of B and C items that do not justify a planner's attention are all strong candidates. For these SKUs, a well-set min and max will quietly do the right thing for months at a time.
The method also fits teams without dedicated inventory planners. A min-max rule is transparent: anyone can look at the two numbers and understand exactly why an order was placed and why it was sized the way it was. There is no forecast model to maintain and no algorithm to explain to your accountant. For an operations team of two or three people managing hundreds of SKUs, that auditability is worth a lot.
Multi-location businesses use min-max for the same reason. Field stock, retail backrooms, and satellite warehouses run well on simple rules because the person closest to the shelf can act on them without waiting for a central planning cycle.
There is a cash-flow benefit hiding in the max, too. Finance teams like min-max because the ceiling puts a hard number on inventory investment per SKU. Multiply every max by unit cost and you have the worst-case cash tied up in stock, a figure most brands running on gut-feel purchasing cannot produce. That makes budgeting conversations between operations and finance shorter and considerably less heated.
The Limits of Min-Max Inventory
Min-max assumes tomorrow looks like the trailing average, and real demand rarely cooperates. A promotion, a seasonal swing, a viral moment, or a retailer reset will blow through a static min before anyone recalculates it. The method has no forward view. If Q4 sells three times what Q2 does, a min set in the spring guarantees stockouts by October unless someone intervenes.
The second failure mode is staleness. Levels get set once, usually during a system rollout or an annual cleanup, and then nobody touches them. Eighteen months later the business has doubled, the supplier's lead time has stretched from two weeks to five, and the min still reflects a company that no longer exists. The math was never wrong; it just stopped being maintained. Lead times deserve particular scrutiny, since supplier variability moves faster than annual reviews and quietly hollows out the buffer your min was built on.
Scale compounds both problems. Min-max across 40 SKUs in one warehouse is a manageable spreadsheet. Min-max across 800 SKUs in three warehouses and two 3PLs is 2,400 SKU-location pairs, each with two numbers that decay at their own rate. At that point brands typically layer real demand planning onto their fast movers and keep min-max for the stable middle and tail, which is exactly the right division of labor.
Keeping Min-Max Levels Current
The difference between min-max working and min-max failing is almost never the formula. It is whether the levels get reviewed. A quarterly recalculation from rolling sales data catches most drift. Faster-moving businesses tie reviews to triggers instead of the calendar: recalculate any SKU whose sales velocity moves more than 25 percent from the rate used to set its levels, or whose supplier lead time changes.
Exception reporting does more good than another meeting. A weekly list of SKUs sitting below min, SKUs stuck above max for 60 days, and SKUs whose levels have not been recalculated in two quarters turns inventory review from an archaeology project into a 20-minute scan.
The step change comes from connecting the pieces. When your inventory counts, sales orders, and purchasing live in one system, a breach of the min does not wait for someone to open the spreadsheet. Stock levels update as orders ship, the system flags the breach the moment it happens, and a draft purchase order sized to the max is ready for approval the same day. Teams running inventory management this way stop losing sales to the gap between a min being crossed and a human noticing.
A Simple Rule Is Only as Good as the Data Behind It
Min-max inventory is the right starting system for most growing product brands: cheap to run, easy to audit, and effective on the steady majority of your catalog. Its failure mode is not the logic. It is stale levels, disconnected data, and manual checks that skip a week when things get busy.
DOSS Operations Cloud closes that gap. It connects inventory, orders, and procurement in one place, keeps stock counts current in real time across warehouses and 3PLs, and turns a min breach into a draft purchase order automatically. It integrates with the tools you already run, and implementation takes months, not years. Book a demo to see min-max replenishment work without anyone babysitting the spreadsheet.
