"Do we need an ERP or an MES?" is one of the most common questions we hear from growing manufacturers. The short answer: they solve different problems, and many factories need a bit of both.
ERP plans the business
A manufacturing ERP runs the business side: sales orders, purchase, inventory, production orders, dispatch, invoicing and accounts. It answers questions like "what do we need to buy?", "what is our stock worth?" and "which orders are due this week?". ERP thinks in days and orders.
MES runs the shop floor
A Manufacturing Execution System (MES) records what actually happens on the shop floor, minute by minute: which operation started, on which machine, by which operator, how many good and rejected parts, what material lot was used and what the quality checks showed. MES thinks in minutes and operations.
Side by side
- Time scale: ERP — days and weeks. MES — minutes and shifts.
- Users: ERP — office, purchase, sales, accounts. MES — operators, supervisors, quality.
- Key output: ERP — orders, stock, invoices. MES — live WIP, OEE, traceability.
- Typical device: ERP — desktop browser. MES — shop-floor tablet or terminal.
Signs you need MES capabilities
- You find out about production problems at the end of the shift.
- Customers ask for lot-level traceability you can't produce quickly.
- Paper route cards get lost or are filled in after the fact.
- Your ERP says an order is "in production" but nobody knows which operation it's at.
You don't need a big-bang project
For SMEs, the most successful approach is usually incremental: start with the module that hurts most — often digital shop-floor booking or production planning — and build outward on the same database. Where you already have an ERP or accounting system, the new modules can exchange data with it where it offers an API or import.
Where MES and ERP overlap
Some functions sit between the two systems and can live in either: production order release, material issue, finished goods receipt, basic quality checks. The question isn't which system "should" own them in theory, but where they are most useful in your factory. A common pattern is: ERP releases orders and manages stock; MES executes operations and reports completions and consumption back.
Integration: how the two systems talk
A typical integration exchanges a few key messages: production orders and BOMs from ERP to MES; operation completions, scrap and material consumption from MES to ERP; and inventory movements in both directions. How this is done depends on your ERP — some provide APIs, others support file import/export. Feasibility should be confirmed early, before scope is fixed.
What if you have neither?
Many SMEs have accounting software and spreadsheets, but neither ERP nor MES. In that case, the right first step depends on the biggest pain. If it's order and stock chaos, start with ERP-style modules (sales, purchase, inventory, production orders). If it's shop-floor visibility, start with MES-style modules (job booking, WIP, downtime). With a custom approach, both grow on the same database over time.
Cost and timeline considerations
Large ERP and MES implementations can take a year or more. For SMEs, phased custom development — weeks per phase, each delivering working software — reduces risk and lets the business learn as it goes. The total scope may be similar, but value arrives much earlier.
Questions to ask before deciding
- Where do we lose the most time and money today — office or shop floor?
- What do our customers demand that we can't currently provide?
- Which data do we wish we had every morning?
- What existing systems must we keep, and what interfaces do they offer?
- Who will own the system on the floor and in the office?
Examples by industry
- Job shop: starts with quotation, job cards and shop-floor booking (MES-like), adds purchase and stock later.
- Distributor-manufacturer: starts with order management and inventory (ERP-like), adds production tracking later.
- Food processor: starts with batch records and traceability (MES-like), connects to existing accounting.
Summary
ERP and MES are complementary. ERP answers "what should we make and what do we need?"; MES answers "what is happening right now and what actually happened?". Most growing manufacturers eventually need capabilities from both. The practical question is where to start — and the answer is wherever your biggest pain is today. Read more in what is an MES.
A practical example
A gear manufacturer receives an order for 2,000 gears due in three weeks. The ERP records the order, checks bar stock, raises a purchase order for shortfall and releases a production order. On the shop floor, the MES guides the order through turning, hobbing, heat treatment (outsourced) and grinding, recording each operation's quantities, rejects, machine time and inspection results. When grinding is complete, MES reports 1,960 good gears back to the ERP, which updates stock, and the order is invoiced. Each system does what it is best at, and together they give a complete picture.
Data ownership and reporting
When MES and ERP are separate, decide which system is the "source of truth" for each piece of data — stock levels, order status, costs — to avoid conflicting reports. A simple rule: ERP owns financial and commercial data; MES owns operational and shop-floor data; reports that need both pull from both. Getting this right early prevents confusion later.
Frequently asked questions
Can one system do both MES and ERP?
Yes. Custom systems often combine ERP-style modules (orders, purchase, stock) and MES-style modules (job booking, WIP, downtime) on one database.
Which should we implement first?
Start where the biggest pain is: office chaos around orders and stock suggests ERP-style modules; lack of shop-floor visibility suggests MES-style modules.
Explore our MES software, manufacturing ERP and 50 manufacturing solutions — or ask us where to start.
