What Is MPS (Master Production Schedule)?
Also known as: master production schedule, master schedule
Definition
An MPS (master production schedule) is the time-phased statement of which end items a plant will produce, in what quantities, and in which periods. It is the anchor demand input MRP explodes into component requirements.
MPS (Master Production Schedule) Explained
The master production schedule sits between the aggregate sales and operations plan and the detailed material plan. Sales and operations planning decides volume by product family in months; the master production schedule breaks that into specific end items by week or day. It is a build plan, not a forecast and not a shipment plan. The distinction matters because the schedule must be feasible: it reflects what will be produced, after demand has been reconciled against capacity and material reality.
Demand time fences and planning time fences govern how the schedule behaves over the horizon. Inside the demand time fence, actual customer orders drive the schedule and the forecast is ignored, because commitments are firm and changes are disruptive. Beyond the planning time fence, the system may create and reschedule planned orders freely. Between the two, changes require planner approval. Setting these fences to match real material and capacity commitment points is one of the highest-leverage configuration decisions in an ERP implementation.
Available to promise is calculated directly from the master production schedule, and rough cut capacity planning validates it against key resources before MRP consumes it. This is the closed loop in action: if rough cut capacity shows the schedule exceeds bottleneck hours, the correct response is to reschedule the master production schedule, not to release it anyway and let the shop sort it out. A schedule that is never rejected is a schedule that is not being validated.
A frequent misconception is that master scheduling is unnecessary in a make-to-order shop because customer orders are the schedule. In practice, even pure make-to-order plants benefit from master scheduling at the level of common sub-assemblies or long-lead components, so those items are being built or bought ahead of the order that will eventually consume them. That is the essence of a planning bill and a two-level master schedule.
Why It Matters
- The master production schedule is the single demand input to MRP, so its stability determines whether the material plan churns weekly.
- Available to promise is derived from it, meaning customer date commitments are only as good as the schedule behind them.
- Time fences configured here control how much nervousness propagates into purchasing and the shop floor.
- A validated master schedule is where sales commitments and plant capacity are reconciled before either side is over-committed.
In Practice
Worked example: a plant sets its demand time fence at two weeks but its longest component lead time is 10 weeks. Orders entering at week three are treated as freely changeable even though the material is already bought. Align the demand time fence with cumulative lead time on the critical components, or accept a steady stream of excess and expedite charges.
Frequently Asked Questions
What is the difference between MPS and MRP?
The master production schedule states what finished items will be built and when. MRP takes that statement, explodes it through bills of materials, and calculates the component and raw material orders needed to support it. The master schedule is a management decision about independent demand items; MRP is a calculation about dependent demand.
What is a demand time fence?
A demand time fence is the near-term boundary inside which the system uses only actual customer orders and ignores forecast, because material and capacity are already committed. Changes inside the fence typically require manual approval. Setting it too short lets the system reschedule work that is physically underway; setting it too long makes the plan unresponsive to real demand.
Related Terms
MRP (Material Requirements Planning)
MRP (Material Requirements Planning) is the ERP calculation that explodes demand through bills of materials, nets it against on-hand and on-order inventory, and offsets by lead time to produce timed purchase and work order suggestions.
Demand Planning
Demand planning is the process of forecasting future customer demand by combining statistical analysis of shipment history with sales, marketing, and customer intelligence, producing the consensus demand signal that drives master scheduling and MRP.
ATP (Available to Promise)
ATP (available to promise) is the portion of inventory and scheduled production not yet committed to existing customer orders, calculated by date so order entry can quote a delivery a customer can rely on.
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