What is inventory planning?
Inventory planning is the process of setting stock levels for each item and location so that orders ship on time without tying up more cash than necessary. The planner works from a demand forecast, the supplier’s lead time, and a target service level, such as the share of order lines filled from stock.
Those inputs produce the settings that drive replenishment in the enterprise resource planning (ERP) or planning system. Safety stock covers uncertainty in demand and lead time. The reorder point is the stock level that triggers a new order, usually the expected demand during the lead time plus safety stock. The order quantity balances the cost of placing orders against the cost of carrying stock. Items are segmented into groups such as fast, slow, and intermittent movers, because each group needs a different policy.
Why inventory planning matters
Inventory is one of the largest assets a distributor or retailer holds. Too little stock loses sales and customers. Too much stock ties up cash and warehouse space and ends in markdowns or write-offs. The settings that govern this balance are frequently years old and maintained by hand.
Machine learning improves the inputs. Demand forecasting models use promotions, seasonality, customer order patterns, and weather. Probabilistic forecasts give a range of likely demand that sets safety stock directly, replacing rules of thumb. Lead-time models learn from each supplier’s actual delivery history instead of the quoted figure in the item master.
Inventory planning in practice
An industrial supply distributor carries tens of thousands of items across four branches, and most of them sell only a few times a year. Buyers reordered from fixed minimum and maximum levels set when each item was added. The company rebuilt the settings from three years of sales and receipts, using a forecasting method suited to intermittent demand and lead times measured from actual deliveries. An agent now drafts the weekly purchase orders with the reason for each line, and a buyer reviews and releases them in the ERP. Buyers spend their time on exceptions such as new items, supplier delays, and large project orders.
What to watch for
- Clean the item master first, since wrong units of measure, duplicate items, and stale lead times will undermine any model.
- Set service levels by item segment with sales and finance, because one target for every item wastes cash on slow movers.
- Recorded sales understate demand during stockouts, so treat those periods separately when training forecasts.
- Keep a buyer’s approval on every purchase order an agent creates, and log the reason for each quantity.