MRP II (Manufacturing Resource Planning) is an integrated planning approach that goes beyond classic material requirements planning. While MRP only calculates which materials are needed in what quantity and when, MRP II additionally considers capacities, lead times, costs – and critically, the feedback of real production data into the planning process.
The goal: a realistic, coordinated production plan that balances demand, capacity, material and costs.
MRP focuses on material requirements – inputs are bills of materials, inventory and orders, outputs are purchase and production order proposals. Capacity is barely considered. MRP II extends this with capacity planning, fine-tuning and a closed feedback loop between planning, execution and actual data. ERP covers finance, sales, procurement and HR in addition – MRP II logic is typically a module within it.
S&OP balances demand and capacity over a medium horizon, producing a coordinated volume plan at product family level. MPS (Master Production Schedule) translates this into concrete production quantities per product and period. MRP derives material requirements via bills of materials and generates order proposals. CRP (Capacity Requirements Planning) checks whether those orders are feasible given available machine and personnel capacities. Shopfloor feedback closes the loop: actual cycle times, downtime, scrap and OEE feed back into planning parameters.
What distinguishes MRP II from static planning is the closed feedback loop. Planning generates orders, the shopfloor executes them, actual data is reported back, planning parameters are adjusted. A plan calculated once a month in the ERP that has nothing to do with reality afterwards is not MRP II – it is a wish list.
This is where the MES connection becomes critical: ERP and APS run the planning logic, the MES supplies the actual data – output, OEE, failures, quality losses – that iteratively make planning parameters like lead times and capacity assumptions more realistic. Without this feedback, MRP II remains theory.
Is MRP II outdated because ERP exists? No. ERP systems implement MRP II logic – the term describes the concept of an integrated, closed production planning process. This approach is more relevant than ever because product variety and volatile markets require exactly this synchronization of planning and execution.
What is the difference between MRP II and APS? APS extends MRP II logic with optimization-based detailed scheduling and complex constraints such as changeover matrices, campaigns and sequencing. MRP II remains the foundation for requirements and capacity logic – APS resolves the conflicts that MRP II makes visible.
Why does MRP II often fail in practice? Almost always because of poor master data: lead times estimated once and never validated, capacities based on theoretical availability, missing shopfloor feedback. MRP II is only as good as the data flowing into it.