MRP vs ERP (and MRP II): Key Differences, Comparison Table and Worked Example

MRP (material requirements planning) calculates what materials to buy or make, how many, and when, from the master schedule and bill of materials. ERP (enterprise resource planning) runs the whole business: MRP plus accounting, sales, purchasing, HR and reporting. MRP II sits between them, adding capacity and cost to MRP.

That is the short answer to MRP vs ERP. The rest of this page puts MRP, MRP II, ERP and APS side by side in one table, runs one small order through all four so you can see what each adds, and ends with how to choose. If you only need the MRP mechanics, start with what MRP is and how the calculation works. For the full reference, see our complete MRP guide.

Written by User Solutions, Inc., makers of EDGEBIC (RMDB 2.0) by User Solutions, planning and scheduling software for manufacturers since 1991. Reviewed by the User Solutions planning team. Updated September 2026.

MRP vs MRP II vs ERP vs APS: comparison table

The two rows that matter most are material planning and capacity. MRP and a standard ERP run both assume the plant can absorb whatever the plan asks for. APS is the only column that checks real hours. That is why many plants run an ERP for the business and add a scheduling layer for the shop. For that split in more depth, see APS vs ERP scheduling and MRP vs APS.

MRP vs ERP: the key differences

MRP and ERP are not competitors. ERP contains MRP. The practical question is whether you need the rest of what ERP brings.

If your problem is "we run out of parts" or "we order too much," MRP is the tool. If your problem is "sales, the shop and accounting all keep their own spreadsheets," that is an ERP problem. If your problem is "the plan looks fine but jobs are late," neither solves it on its own: that is a capacity problem, and it needs finite capacity scheduling.

MRP I: Where It All Started

Material Requirements Planning, or MRP I, originated in the 1960s when Joseph Orlicky at IBM formalized the logic for calculating material requirements based on dependent demand. Before MRP, manufacturers relied on reorder point systems that treated every part independently, leading to chronic stockouts of some items and overstocking of others.

What MRP I Does

MRP I is fundamentally a material calculator. It takes three inputs and produces time-phased material plans:

From these inputs, MRP I calculates net requirements, determines order quantities using lot sizing methods, and time-phases orders by offsetting lead times. The step-by-step arithmetic is in what is MRP.

What MRP I Does NOT Do

• No capacity planning. MRP I assumes infinite production capacity. It will happily schedule 1,000 hours of work in a week on a machine that only has 40 available hours.
• No shop floor control. It generates planned orders but does not help sequence or track work on the factory floor.
• No financial integration. Material plans are disconnected from cost accounting and budgeting.
• No demand management. It takes the MPS as given and does not help create or validate it.

This is why manufacturers who rely solely on MRP I often find their material plans are technically correct but practically impossible to execute. The materials arrive on time, but the shop floor cannot process them because capacity was never considered.

ERP: Enterprise Resource Planning

In the 1990s, software vendors like SAP, Oracle, and Baan recognized that manufacturers needed to connect production planning with every other business function. Enterprise Resource Planning, or ERP, was born by extending MRP II's manufacturing focus to encompass the entire enterprise.

What ERP Adds Beyond MRP and MRP II

ERP includes everything in MRP II plus:

• Financial accounting and reporting (general ledger, accounts payable/receivable, asset management)
• Human resources (payroll, benefits, workforce management)
• Customer relationship management (sales pipeline, customer history, quoting)
• Supply chain management (procurement, logistics, warehouse management)
• Business intelligence (dashboards, analytics, executive reporting)
• Multi-site and multi-currency support for global operations

The ERP Trade-Off

ERP's breadth comes at a cost. Compared with a focused planning and scheduling tool:

This trade-off is why many manufacturers choose a hybrid approach: keep their existing accounting and business systems, and add a specialized MRP and scheduling tool for production planning. RMDB from User Solutions, now EDGEBIC (RMDB 2.0), is designed exactly for this approach, integrating with SAP, Oracle, Epicor, Sage, and other systems as an ERP scheduling add-on.

MRP II: Manufacturing Resource Planning

In the 1980s, Oliver Wight and others recognized that material planning alone was insufficient. They expanded the MRP concept into Manufacturing Resource Planning, or MRP II, which added capacity and financial dimensions to the planning process. MRP II is the bridge between MRP and ERP: ERP is essentially MRP II with the rest of the business attached.

What MRP II Adds Beyond MRP I

MRP II includes everything in MRP I plus:

Capacity Requirements Planning (CRP). MRP II checks whether your material plan is feasible given your available machine hours, labor hours, and other resources. When MRP says you need to produce 500 units in Week 4, CRP verifies whether you actually have the capacity to do so.

Shop Floor Control. MRP II tracks work-in-progress, monitors job status against the plan, and provides feedback on actual versus planned performance. This creates a closed-loop MRP system where shop floor reality feeds back into planning.

Demand Management. MRP II includes tools for forecasting, order entry, and creating the master production schedule. Rather than taking the MPS as given, MRP II helps build it.

Financial Planning. MRP II connects production plans to financial projections. When you plan to produce 1,000 units next month, MRP II can calculate the associated material costs, labor costs, and expected revenue.

Simulation and What-If. MRP II allows planners to test scenarios before committing to a plan. What happens to capacity if we accept a rush order? What if a supplier lead time doubles?

MRP I vs MRP II Comparison

Note that CRP in most MRP II and ERP systems reports overloads rather than fixing them. It tells you a work center is at 125% and leaves the planner to decide what moves. That gap is what APS closes.

Worked example: one order through MRP, MRP II, ERP and APS

A shop must ship 100 tables in week 6. Each table uses 4 legs and 1 top. Final assembly takes 0.5 hours per table, and the assembly bench has 40 hours a week (one 8-hour shift, 5 days).

MRP nets and offsets. Legs: 400 - 120 = 280 to order, released in week 4 (6 - 2). Tops: 100 - 30 - 20 = 50 to order, released in week 3 (6 - 3). Material is covered, and MRP says nothing else.

MRP II adds the capacity check. Assembly needs 100 x 0.5 = 50 hours in week 6 against 40 available, a load of 50 / 40 = 125%. CRP flags the 10-hour overload but does not move anything.

ERP carries the same MRP and CRP results and adds the business side: the two purchase orders go to purchasing and accounts payable, the sales order is visible to customer service, and inventory is valued in the ledger. The overload is still there.

APS fixes the overload. The bench fits 40 / 0.5 = 80 tables in week 6, so the scheduler starts the other 20 tables (10 hours) in week 5. Materials still work: week 5 needs 80 legs and 20 tops, covered from the 120 legs and 30 tops on hand. Week 6 then needs 320 legs and 80 tops; after week 5 there are 40 legs and 10 tops left, plus the 20 tops due in week 3, so the orders stay at 320 - 40 = 280 legs and 80 - 30 = 50 tops. Nothing is late.

The point of the example: MRP got the parts right, MRP II and ERP noticed the problem, and only finite scheduling produced a plan the shop could run. When the parts are tight, an APS with MRP built in (EDGEBIC Complete pegs material to each order) checks both at once.

How to Choose: MRP vs ERP (and MRP II)

The right choice depends on your operation's complexity, existing systems, and primary pain points.

Choose MRP-Level If:

• Your primary challenge is material shortages and ordering timing
• You produce relatively simple products with predictable demand
• You have fewer than 50 employees
• You already have accounting software that works well
• Budget is a primary concern

A focused option is described on our MRP software for small manufacturers page.

Choose MRP II-Level If:

• You need both material planning and capacity planning
• Shop floor visibility and scheduling are critical
• You need finite capacity planning to sequence work realistically
• You produce complex products in a make-to-order or custom manufacturing environment
• You want closed-loop feedback between planning and execution

Choose Full ERP If:

• You have disconnected systems causing data silos across the business
• You need integrated financial, HR, and CRM capabilities
• You operate multiple facilities or in multiple countries
• Your current systems cannot scale with your growth
• You have the budget and timeline for a major implementation

The Best of Both Worlds

Many manufacturers find the sweet spot by combining a focused scheduling and MRP tool with their existing business systems. This gives you the deep manufacturing planning capability of MRP II-level software without the cost, risk, and timeline of full ERP.

User Solutions has been serving this exact need for over 35 years. RMDB, continued today as EDGEBIC (RMDB 2.0) by User Solutions, provides finite capacity scheduling, material planning, and visual Gantt-based shop floor management that integrates with your existing ERP or accounting system. EDGEBIC Complete ($35,000 one-time) adds MRP, inventory, purchasing and material pegging; see the MRP system page. The one-time license model means no recurring subscription costs.

The Modern Landscape: Beyond the Traditional Labels

In 2026, the MRP vs ERP distinction is increasingly blurry. Modern manufacturing software falls along a spectrum rather than into neat categories:

Cloud MRP tools (like MRPeasy, Katana, and others) offer MRP with light MRP II features like basic capacity planning and shop floor tracking. They are affordable but may lack depth for complex manufacturing.

Advanced Planning and Scheduling (APS) tools like RMDB combine finite capacity scheduling with MRP logic. They go deeper than basic MRP on the planning side while integrating with existing systems for business functions.

Modern ERP platforms (NetSuite, SAP Business One, Epicor Kinetic) bundle everything together but require significant investment and customization to match your processes.

Best-of-breed integration is the growing trend, where manufacturers pick the best tool for each function and connect them through APIs. This approach gives you manufacturing planning depth without ERP bloat.

The best MRP software for small manufacturers often lives in the APS or focused MRP category rather than full ERP, because these tools solve the specific problems small manufacturers face without the overhead of enterprise systems.

Key Takeaways

If your primary pain is production planning, scheduling, and material management, a focused MRP II-level tool will deliver faster ROI than a full ERP implementation. If your business systems are truly broken across the board, ERP may be warranted, but go in with realistic expectations on timeline and cost.

Frequently Asked Questions

Find the Right Planning System for Your Operation

Whether you need MRP, MRP II, or something in between, User Solutions has been helping manufacturers make the right choice for over 35 years. RMDB, now EDGEBIC (RMDB 2.0) by User Solutions, combines finite capacity scheduling with material planning in a tool built for real-world manufacturing, with a one-time license: $25,000 for EDGEBIC APS or $35,000 for EDGEBIC Complete.

Schedule a free demo to see which level of planning capability fits your operation.