Demand planning and inventory management: how they connect

Demand planning decides how much you expect to sell. Inventory management decides how much stock you hold, where and when. When the two run apart, the forecast says one thing and the stock says another, and the gap shows up as overstock in some places and stockouts in others. When they run together, every buy and every re-order starts from the same view of demand.

How demand planning reduces inventory costs

Most inventory cost comes from holding the wrong stock: too much of what doesn't sell, too little of what does. Demand planning cuts that cost in three places.

• Overstock. A forecast cleaned for one-off promotions and past stockouts stops the buy being set from an inflated baseline.
• Markdowns. Re-forecasting in season shows early which lines are slowing, so intake can be cut before the excess has to be cleared at a discount.
• Holding cost. Matching intake to expected sales week by week keeps cover at the level the business needs, not weeks above it, which frees up cash and space.

Can demand planning reduce stockouts?

Yes, when it is connected to replenishment and allocation. A forecast by store, week and size shows where cover will run out before it does. Replenishment raises the re-order against the supplier's real lead time, and allocation sends the stock to the stores where it will sell. A forecast on its own doesn't prevent a stockout. The stock arriving in time does.

Inventory planning vs demand forecasting

• Demand forecasting estimates what customers will buy: by product, store and week, from sales history and what has changed since.
• Inventory planning decides what stock to hold to meet that demand: how much to buy, when it should land, how much cover to keep and where it goes.

The forecast is an input. The inventory plan is the decision made from it, inside the budget and open-to-buy.

How the two connect in a weekly planning cycle

1. Monday: sales and stock from the week before update the forecast.
2. The re-forecast flows into the MFP (WSSI), showing where sales, stock and intake are off plan.
3. Planners review the exceptions: lines running out of cover, lines with too much stock, orders arriving late.
4. Decisions follow: re-orders through replenishment, stock moved between stores, intake cut or brought forward, markdowns where needed.
5. The ERP is updated with the approved changes, and stays the system of record.

In merchmix, demand forecasting, the MFP (WSSI), open-to-buy and replenishment run in one system, so this cycle happens on one set of numbers. You can test it on your own data in a free six-week proof of concept, with no contract.

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FAQ

How does demand planning help reduce inventory costs?
By setting buys from a forecast cleaned for promotions and past stockouts, re-forecasting in season so intake is cut before excess builds up, and keeping weeks of cover at the level the business needs. That means less overstock, fewer markdowns and less cash tied up in stock.

Can demand planning reduce inventory stockouts?
Yes, when it feeds replenishment and allocation directly. The forecast shows where cover will run out, replenishment raises the order in time for the supplier's lead time, and allocation sends the stock where it will sell.

What is the difference between inventory planning and demand forecasting?
Demand forecasting estimates what customers will buy. Inventory planning decides what stock to hold to meet it: how much to buy, when it lands and where it goes. The forecast is the input, and the inventory plan is the decision made from it.