Dependent Demand — Manufacturing Glossary

Dependent demand is demand for a component or material that is directly derived from the production schedule of its parent item. In manufacturing, dependent demand is calculated through Bill of Materials (BOM) explosion rather than forecasted independently. It is the fundamental concept that makes Material Requirements Planning (MRP) possible.

At User Solutions we explain dependent demand as the cornerstone principle that separates modern MRP-driven planning from the old days of guessing how many parts to order.

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How Dependent Demand Works

Dependent demand flows downward through the BOM hierarchy. When the master production schedule specifies a quantity of finished goods, MRP explodes the BOM to calculate the exact quantity of every sub-assembly, component, and raw material required.

The key insight: dependent demand items do not need to be forecasted because their demand is mathematically determined by the parent item's schedule.

The Calculation Chain

1. The master production schedule sets demand for the finished product (this is independent demand).
2. MRP explodes the BOM to determine component quantities.
3. Each component's demand depends on — and is calculated from — the parent quantity.
4. The process repeats down through every BOM level until raw materials are reached.

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Dependent Demand Example

A manufacturer produces industrial gear pumps. The BOM for one pump (GP-500) includes:

• 1 pump housing
• 2 gear shafts
• 4 bearings
• 8 bolts
• 1 seal kit

The master production schedule calls for 150 pumps in Week 10.

MRP calculates dependent demand:

These quantities are precise — no forecasting required. MRP then subtracts on-hand inventory and scheduled receipts to compute net requirements.

If the warehouse holds 80 bearings and 200 are due from a supplier in Week 9, net requirements for bearings = 600 - 80 - 200 = 320 bearings to order.

Notice that changing the parent schedule to 200 pumps would automatically recalculate every component. This cascading recalculation is the power of dependent demand planning.

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Why Dependent Demand Matters for Scheduling

Eliminates guesswork for component planning. Instead of forecasting hundreds of individual parts, planners forecast only finished goods and let MRP calculate everything else. This dramatically reduces planning effort and error.

Synchronizes material arrivals with production. Because dependent demand is time-phased (tied to the parent's scheduled start date), materials arrive when needed — not too early (tying up cash) or too late (stopping production).

Reduces inventory costs. Manufacturers that properly leverage dependent demand through MRP typically carry 20-30% less component inventory than those using reorder-point systems for every part. The savings come from ordering exactly what is needed, when it is needed.

Enables accurate scheduling. Scheduling software like Resource Manager DB uses dependent demand calculations to ensure materials are available before scheduling a job. No materials, no point scheduling the work.

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Related Terms

• Independent Demand — Demand from external customers that must be forecasted, as opposed to calculated dependent demand.
• Bill of Materials (BOM) — The structured list that defines the parent-child relationships used to calculate dependent demand.
• Gross Requirements — The total dependent demand for a component before netting out inventory and receipts.

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FAQ

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This term is part of the Manufacturing Glossary. For a deep dive into material planning, see our MRP Guide.