An MES (manufacturing execution system) is software that runs and records production on the plant floor in real time. It takes the orders the ERP planned, dispatches them to lines and operators, records what was actually made, scrapped and stopped, and reports it back to the ERP. In the ISA-95 standard it sits at Level 3, between the ERP at Level 4 and the machine controls below.
Most plants still run without one: IoT Analytics estimates that just 8% of plants worldwide use a commercial MES, and 54% managed operations with pen, paper or spreadsheets in 2024. The supply side is just as fragmented: more than 300 vendors, with the global leader holding less than 10% of the market. If you are shopping for one, go straight to the best MES software for 2026.
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In this guide
What is an MES system, in one definition?
What does MES stand for?
Where does an MES sit in ISA-95?
What are the 11 functions of an MES?
How does an MES work on one work order?
What are examples of MES systems?
What is the difference between MES and ERP?
How is an MES different from SCADA and MOM?
When does a plant need an MES?
What does an MES not do?
What is an MES system, in one definition?
The clearest definition dates from 1999, when the US National Institute of Standards and Technology (NIST) adapted the definition in the Object Management Group’s MES request for information: “A Manufacturing Execution System is a collection of hardware/software components that enables the management and optimization of production activities from order launch to finished goods. While maintaining current and accurate data, an MES guides, initiates, responds to and reports on plant activities as they occur” (NIST, 1999). IBM’s current version (updated 18 June 2026) is shorter: “a type of software used to monitor and control production processes on the shop floor.”
A plain test tells the systems apart. “What should we make this month, and do we have the material?” is an ERP question. “What is Press 3 running right now, how many good parts so far, and why did it stop at 2:10?” is an MES question. NIST added the sentence every buyer should keep: “MES should be defined by a set of functions, not a set of software packages.”
What does MES stand for?
MES stands for manufacturing execution system. Two traps sit in the search results. “MES” also means “monitoring and evaluation system” in aid and development programs, which is unrelated software. And some vendors now say MOM (manufacturing operations management) for a broader product that includes an MES, covered below.
The body that defined the MES no longer exists. MESA International ceased operations effective 30 June 2026, and ISA assumed its educational programs and content. Khris Kammer, Chairman of MESA International, in ISA’s announcement: “ISA is a global tax-exempt organization whose standards, including ISA-95 and ISA-88, form the technical foundation of much of MESA’s educational work.”
Where does an MES sit in ISA-95?
ISA-95, published internationally as IEC 62264, places plant software on five levels taken from the Purdue Reference Model. ISA states that the standard defines “the interface between control functions and other enterprise functions,” and that “the interface initially considered is the interface between levels 3 and 4” (ISA95 committee).
Level 4, business planning and logistics: ERP, MRP, WMS. Orders, purchasing, inventory, costing. Days to months.
Level 3, manufacturing operations management: the MES, plus QMS (quality) and CMMS (maintenance). What runs where, in what order, with what result. Shifts to seconds.
Level 2, monitoring and supervisory control: SCADA, HMI, DCS. Real time.
Level 1, sensing and manipulating: PLCs, sensors, drives. Real time.
Level 0, the physical process: presses, CNC machines, ovens, lines.
Level 3 is the whole operations layer, not only the MES. The MES is its production part, and quality and maintenance systems sit beside it. For all twelve kinds of plant software on this map, read manufacturing software explained.
What are the 11 functions of an MES?
MESA International set out the “MESA-11” model in White Paper 6, “MES Explained: A High Level Vision,” dated September 1997. The surviving primary source is NIST’s 1999 response, which quotes each function “as it appears in Appendix A of MESA white paper 6.”
Resource allocation and status: are the machine, tool, operator and material ready for this job?
Operations/detail scheduling: the job sequence on each machine inside the shift.
Dispatching production units: pushing the next job, lot or batch to the line.
Document control: the right drawing, instruction and spec at the station.
Data collection/acquisition: counts, times, readings and reason codes, from machines and people.
Labor management: who worked which station, for how long, with which certification.
Quality management: in-process checks, holds and nonconformances as they happen.
Process management: watching the process against its limits.
Maintenance management: equipment status and maintenance as it affects production.
Product tracking and genealogy: which lot went into which part on which machine.
Performance analysis: actual against plan in the shift, including OEE.
NIST itself recommended “the deletion of the Process Management function from the MES function list,” treating it as a control-layer job. Few plants need all eleven. Some practitioners start with a “Core 4,” per IoT Analytics: work-order management, production scheduling, downtime tracking and OEE.
How does an MES work on one work order?
Follow one illustrative order. A plant makes a steel bracket, and the customer wants 500 by Thursday.
ONE WORK ORDER, ONE SHIFT
What an MES does between the ERP's order and the ERP's confirmation
STEP 01
Release
The ERP releases work order 4471: 500 brackets, routing blank, press, deburr, inspect.
06:00
The ERP's job is done until it hears back
STEP 02
Schedule
The MES sequences 4471 on Press 3 after the running job, because die 114 is staged and the operator is certified.
06:05
Resource status and detail scheduling
STEP 03
Dispatch
The operator's screen shows 4471, 500 pieces and drawing revision C. A coil scan confirms the material.
06:40
Dispatch and document control
STEP 04
Collect
Strokes counted from the press controller, scrap logged with a reason, a die change logged as 25 minutes down.
06:40 TO 14:35
Data collection and performance
STEP 05
Hold
A dimension check fails. The MES holds the last 40 pieces: 38 scrapped, 2 reworked.
14:40
Quality management and genealogy
STEP 06
Confirm
The MES sends 462 good, 38 scrap, labor hours and genealogy to the ERP. The order is 92% complete.
18:00
Inventory and costing update
Illustrative example. Times and counts are invented to show the functions.
Every step is a fact recorded as it happened. The MES did its job well. The customer still needed 500, and nothing in the MES asks anyone to decide what happens to the 38 missing brackets.
What are examples of MES systems?
Four products anchor the category: Siemens Opcenter Execution, sold in six industry editions; SAP Digital Manufacturing, which SAP calls “a manufacturing operations management (MOM) platform”; AVEVA Manufacturing Execution System, a “hybrid cloud MES”; and Plex MES from Rockwell Automation, a “cloud-based production management platform.” None of the four publishes a price; all are quote only. Leadership is vertical: IoT Analytics’ MES market report (December 2025) names Körber in pharmaceuticals, Rockwell in automotive and food and beverage, Siemens in electronics and Applied Materials in semiconductors, with “9 different vendors” leading the 13 industries it analyzed.
By plant type, the MES does different work:
Discrete (machining, fabrication, assembly): routings, work instructions, serial or lot traceability, good parts per operation.
Process and batch (chemicals, food, glass): recipes, batch records, what went into the vessel and what came out.
Regulated (pharma, medical devices, aerospace): the electronic batch record or device history record, signed.
Vendors, prices and picks by plant type are in the best manufacturing execution system software.
What is the difference between MES and ERP?
The ERP plans and records the business: sales orders, purchasing, inventory, costing and the master plan, in days and months, at ISA-95 Level 4. The MES runs and records the floor: what is running, what was made and scrapped, and why the line stopped, in minutes and shifts, at Level 3. The ERP releases the order; the MES executes it and confirms back. Most plants above a line or two end up with both, connected.
Patrick Austin, President of Midwest Precision Molding, told IndustryWeek why his plant stopped tracking the floor in its ERP: “[The ERP system] didn’t have the capabilities to hook up to real-time [data capture], like the current MES system does.” Connection is still the weak point: Rockwell Automation’s July 2026 survey of 1,560 manufacturers found 93% have an MES but only 23% report full integration with ERP, PLM, quality and OT systems. The full comparison is at MES vs ERP.
How is an MES different from SCADA and MOM?
SCADA (supervisory control and data acquisition) sits at Level 2. It supervises equipment and gathers readings in seconds; its unit of work is a tag or an alarm. The MES sits at Level 3 and its unit of work is an order or a lot. SCADA is one of the sources an MES reads: IBM lists “supervisory control and data acquisition (SCADA) tools” among the ways an MES connects to the floor.
MOM is the name of the whole of Level 3. SAP puts it plainly: “MOM covers a broader scope than a manufacturing execution system (MES).” A product labeled MOM bundles the MES with quality, maintenance and inventory operations. Ask which of the eleven functions it actually performs.
Is SAP an MES? SAP the company sells one, SAP Digital Manufacturing. SAP’s ERPs, S/4HANA and Business One, are not an MES; they sit at Level 4.
When does a plant need an MES?
A plant with an ERP, a few stable lines and a good supervisor can run on paper travelers for a long time. These are the signs that it has stopped working:
You cannot say how many good parts each line has made this shift without walking the floor.
The first hour of every morning goes to reconstructing yesterday.
“Which lot went into this part?” takes days to answer.
Scrap and downtime are known as totals, not causes.
The ERP’s inventory is wrong by the afternoon because confirmations arrive in a batch.
OEE is a spreadsheet built from numbers someone wrote down.
If none of these apply, put the money into connecting the systems the plant already has. For a lighter first step, see shop floor management software.
What does an MES not do?
An MES keeps the floor’s record. It does not decide what happens next. At 18:00 on the bracket order, the MES and the ERP agree: 462 good, 38 scrap. Neither system is wrong. But purchasing does not know about the shortfall, planning will see it at the next MRP run, and whether 38 more get made before Thursday depends on someone reading a message in the shift group and acting on it. The data is complete. What is missing is coordination. No system connects a floor event to the customer order it affects and gets a person to act before the date.
That gap is the work Morsa runs. Morsa is the AI that operates the factory for you: it runs the daily operations work of mid-market and enterprise manufacturers, from supplier follow-up to replanning, on top of the MES, ERP and channels the plant already uses, and it never replaces them. At J4S, a 120-person glass plant, on-time completion of operational commitments went from about 30% to about 75% in the first four weeks. It went live in two days with no new software (the J4S story). Anil Kohli, Production Head at J4S: “Our people don’t have to learn any new software. People just message the way they always have. Morsa coordinates all the messages in the background.” More on what autonomous manufacturing looks like day to day.
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Sources
NIST, Barkmeyer, Denno, Feng, Jones and Wallace, “NIST Response to MES Request for Information,” 6 December 1999 (definition, functions-not-packages sentence, MESA-11 quoted from MESA White Paper 6, Process Management recommendation). nist.gov
IBM, Josh Schneider and Ian Smalley, “What is a manufacturing execution system (MES)?”, updated 18 June 2026. ibm.com
IoT Analytics, Anand Taparia, “MES vendors replace pen, paper, and spreadsheets,” 15 December 2025, and the MES Market Report 2025-2031 page (vertical leaders). iot-analytics.com, report page
ISA, ISA95 committee: scope and purpose. isa.org
ISA, “ISA Announces Assumption of MESA International Educational Programs and Content,” 30 June 2026. isa.org
Rockwell Automation, “93% of Manufacturers Have MES, But Only 23% Have Fully Integrated It,” 14 July 2026 (vendor research, n=1,560). rockwellautomation.com
IndustryWeek, Dennis Scimeca, “Switching from ERP to MES Drives Improvement for Plastics Manufacturer,” 15 December 2023. industryweek.com
SAP, SAP Digital Manufacturing product page, read 24 September 2026. sap.com
Product pages read 24 September 2026: Siemens Opcenter Execution, AVEVA MES, Plex MES
Changelog
24 September 2026: tightened into a definitional guide for “what is an MES system”: the definition now leads, the 11 functions are one line each, the worked shift is a six-step figure, and MES vs ERP, SCADA and MOM are condensed. Vendor shopping moved to the MES software guide. Removed customer claims we could not verify and the old positioning of Morsa; Morsa is now described as the AI that operates the factory for you, and its section links to the autonomous manufacturing guide.
20 September 2026: corrected the attribution of the MES definition to NIST’s adaptation of MESA’s; added adoption figures from IoT Analytics and Rockwell.
