Master Production Schedule (MPS)
📅 The build plan for end items
Horizon	Cumulative lead time + 1–2 months
Time bucket	Weekly (sometimes daily)
Key input	S&OP production plan, customer orders, forecast
Key output	Time-phased production quantities per end item
Feeds into	MRP, CRP
Part of	MRP II

Master Production Schedule (MPS)

The Master Production Schedule (MPS) is the central plan in MRP II that states what end items will be produced, how many, and when. Often called the "anticipated build schedule," it translates the aggregate S&OP production plan into specific item-level, time-phased quantities. The MPS is the primary input to both Material Requirements Planning and Capacity Requirements Planning.

Contents

Role in MRP II
The MPS grid
Available-to-Promise (ATP)
Time fences
Relationship to other modules
See also

Role in MRP II

The MPS is the bridge between strategic planning (S&OP) and detailed execution (MRP, SFC). It must satisfy three often-conflicting constraints:

Stay within the production rates authorised by S&OP
Meet customer delivery commitments (demand side)
Remain feasible within capacity and inventory constraints (supply side)

The MPS grid

The MPS is typically maintained as a time-phased grid (weekly buckets). For a given item, the key rows are:

Row	Wk 1	Wk 2	Wk 3	Wk 4	Wk 5
Forecast	20	20	20	20	20
Customer Orders	18	14	8	3	0
MPS Quantity	0	50	0	50	0
Projected On-Hand	10	40	20	50	30
ATP	12	36	—	47	—

The greater of forecast and customer orders drives the projected on-hand calculation: POH = Prior POH + MPS Qty − max(Forecast, Orders).

Available-to-Promise (ATP)

ATP tells sales how many units can be promised to new customers without changing the MPS. It is calculated as: ATP = MPS Qty − Customer Orders before next MPS receipt. This is a critical link between the MPS and the sales/order management process, preventing over-commitment.

Time fences

graph LR
    subgraph " "
        direction LR
        FZ["Frozen Zone
(0 to Demand Fence)
No changes without
senior approval"]
        SZ["Slushy Zone
(Demand to Planning Fence)
Changes allowed
with justification"]
        LZ["Liquid Zone
(Beyond Planning Fence)
System can
auto-schedule"]
    end

    FZ --> SZ --> LZ

    style FZ fill:#f5d5d5,stroke:#333
    style SZ fill:#fff3cd,stroke:#333
    style LZ fill:#d5f5d5,stroke:#333

Time fences control who may change the MPS in each horizon:

Frozen zone — Inside the demand time fence (typically = cumulative lead time). Changes here disrupt shop floor and purchasing execution and require senior management approval.
Slushy zone — Between the demand and planning time fences. The master scheduler can make changes but must assess the capacity and material impact.
Liquid zone — Beyond the planning time fence. The system can automatically adjust the MPS based on updated forecasts.

Relationship to other modules

graph TB
    SOP["S&OP"] -->|"production plan"| MPS["MPS"]
    MPS -->|"what & when to build"| MRP["MRP"]
    MPS -->|"planned load"| CRP["CRP"]
    CRP -.->|"feasible?"| MPS
    SFC["SFC"] -.->|"actual production"| MPS

    style MPS fill:#cedff2,stroke:#333