Concept guide, Service and maintenance

What is a CMMS? How maintenance management software works

Author: PureField
Published: 9 November 2026
Updated: 9 November 2026

A CMMS (computerized maintenance management system) is software that keeps each asset's record, maintenance schedule, work orders, spare parts and maintenance history in one place. It answers, from a single record, who serviced which machine, when, and with which parts. It is also called maintenance management software.

What does a CMMS do?

A CMMS ties every maintenance record to the asset: the work order, the schedule, the parts used, the warranty and the manual all sit on the same asset card. Because the record belongs to the asset rather than to a person, the history stays put when the technician who did the work moves on.

The production manager asks when the line's compressor was last serviced and whether the filter was changed. With scattered records, the maintenance lead checks a spreadsheet, then the technician's phone, then the stores issue slip. In a CMMS the answer is the maintenance history on the asset card.

The operations and maintenance guide written for the US Department of Energy's Federal Energy Management Program (FEMP) lists the typical functions of a CMMS. The table groups that list by record and adds basic fields such as serial number and location.

Record	What the CMMS keeps	The question it answers
Asset card	Serial number, location, warranty, manual, maintenance procedure	Where is this machine, and when does its warranty end?
Work order	Date opened, priority, assignee, status, closing note	Who is on the breakdown, and what is its status?
Maintenance schedule	Interval by calendar or run time	When is the next service due?
Maintenance history	Work orders sortable by asset, date and person	Who serviced it last, and when?
Spare parts	Stock, parts used, reorder	Are the parts ready for the job?
Reports	Work in progress, labor and cost per asset, time to close a work order	Which machine stops most, and which costs most?

The same guide describes the job of a CMMS as collecting information and storing it so it is easy to retrieve. The maintenance manager makes the decision with that information.

Which types of maintenance does a CMMS manage?

A CMMS records three types of maintenance: reactive maintenance after a failure, preventive maintenance on a calendar or run-time schedule, and predictive maintenance based on measurements. What triggers the maintenance decides which records the CMMS needs.

Maintenance type	Triggered by	Records the CMMS needs
Reactive (corrective)	A failure	Failure report, work order, repair time, root-cause note
Preventive	Calendar or run time	Interval, next due date, reminder, checklist
Predictive	Measurements or sensor data	Measured value, threshold, measurement date

The FEMP guide defines preventive maintenance as actions on a time- or machine-run-based schedule that detect, preclude or mitigate the degradation of a component or system. Predictive maintenance bases the need for maintenance on the machine's measured condition rather than on a preset schedule.

Citing earlier studies, the guide says preventive maintenance can save as much as 12% to 18% on average over a purely reactive program. Its estimate for predictive maintenance is 8% to 12% over preventive maintenance alone. These are averages from a 2010 guide; your own figure comes from your unplanned downtime and repair records.

Small and mid-sized businesses usually go in this order: first the asset list and the preventive schedule, then measurement data on top of that record-keeping.

How does a CMMS differ from EAM, FSM and ERP?

All four keep maintenance records; they differ in whose equipment they cover and which part of the work they focus on. A CMMS runs maintenance of a company's own equipment, while FSM runs the service visit to equipment at the customer's site.

Software	Whose work	Focus
CMMS (maintenance management)	The in-house maintenance team of a plant, hospital, hotel or building	Asset card, maintenance schedule, work order, spare parts
EAM (enterprise asset management)	Organizations with several sites and a large asset base	The asset's whole life and cost, from purchase to disposal
FSM (field service management)	Companies that service their customers' equipment	Service request, technician assignment, on-site report, invoice
ERP maintenance module	Businesses that run stock, purchasing and accounting in one system	How maintenance links to parts, purchasing and cost records

A field service company needs both. The equipment sits at the customer's site, so its card, warranty and schedule are CMMS work. The technician who goes out to service it works with FSM's work order, mobile report and customer signature. The article What is field service management software? covers that side in detail.

Which metrics does a CMMS track?

The work orders and maintenance records in a CMMS are enough to calculate how often a machine fails and how long it takes to repair. These are the metrics teams track most.

Metric	How it is calculated	What it tells you
MTBF (mean time between failures)	Total operating time / number of failures	How often the machine fails
MTTR (mean time to repair)	Total repair time / number of repairs	How quickly the machine is back after a failure
PM completion rate	Planned maintenance done on time / planned maintenance	Whether the schedule is being kept
Unplanned downtime	Total time the machine was stopped by failures	The impact of failures on production or service
Work order backlog	Number of open and overdue work orders	Whether the team keeps up with the workload

A compressor ran 700 hours in 30 days and failed twice: its MTBF is 350 hours. If the two repairs took 6 hours in total, its MTTR is 3 hours. A falling MTBF points to the maintenance interval; a rising MTTR points to the parts and crew plan.

What should you ask before moving to a CMMS?

To decide whether a CMMS is needed, the FEMP guide suggests looking at how things run today and asking these questions. If the answers are vague, it is time to move maintenance records into one system.

How are work orders opened and tracked, and how do you confirm the work was done correctly?
Can you find when a machine was last serviced, by whom, and in what condition?
How is spare-parts stock managed: is there excess stock, or are you always waiting for parts?
Are maintenance procedures, equipment manuals and warranty documents kept in an organized place?
Where do you look up your equipment list when you report or plan?

The seven criteria to check when choosing the software, and the steps for moving off spreadsheets, are in CMMS software for small and mid-sized businesses.

How does PureField handle CMMS work?

In PureField field service, the maintenance record starts with a QR-coded asset card. The card holds the warranty, the next maintenance date, documents and the service history. Depending on your business, the asset is equipment installed at a customer's site or a machine in your own facility.

Maintenance reminder: When the next maintenance date on the asset card comes up, a reminder email goes to the customer and the service team; your team opens the work order.
Service request and work order: Internal and customer requests are linked to a work order; requests from outside sources become a service request or go straight to a work order.
On-site report: The technician scans the asset's QR code in the mobile app and closes the report with photos, a checklist and signatures. The finished report goes out as a PDF by email, and the invoice is issued from the report.
Service vehicles: Fleet assignment and vehicle maintenance records sit in the same module.
From sale to service: The sales team creates asset cards from quote lines, so the maintenance history of equipment you sold shows on the customer record.

Evidence

FEMP Operations and Maintenance Best Practices Guide, Release 3.0 (US Department of Energy, 2010): Definition of a CMMS (§4.1), questions for assessing the need for a CMMS (§4.2), typical CMMS functions (§4.3), the CMMS role of collecting and storing information (§4.4), definitions of reactive, preventive and predictive maintenance and their savings ranges (§5.2–5.4). Source: pnnl.gov
QR asset card: The asset card opens with QR code, documents, warranty and maintenance date fields.
Maintenance reminder email: A reminder goes to the customer and the service team based on the next maintenance date; the team opens the work order.
Service report and invoice: The finished report goes out as a PDF by email; the invoice is issued from the finished service report.

Add a few of your machines to PureField and enter their next maintenance dates. Book a demo or try it free for 7 days.

Frequently asked questions

What does CMMS stand for?

CMMS stands for computerized maintenance management system. It is also called maintenance management software, and some teams simply call it their maintenance tracking system.

Is a CMMS the same as maintenance tracking software?

They usually describe the same need. Maintenance tracking software tends to stress the schedule and reminders; a CMMS adds work orders, spare parts, cost and reporting records on top.

Should a field service company use a CMMS or field service software?

A company that maintains its customers' equipment needs what both do. The asset card and maintenance schedule come from the CMMS side; the service request, technician assignment and signed on-site report come from field service software. In PureField these records link to the same customer record.

What data do you need to start with a CMMS?

For each machine, a name, serial number, location, last maintenance date and maintenance interval are a good start. Warranty end dates, manuals and past service reports can follow. Starting with critical equipment and growing the list keeps data entry manageable.

How do you calculate MTBF and MTTR?

MTBF is total operating time divided by the number of failures; MTTR is total repair time divided by the number of repairs. A machine that ran 700 hours and failed twice has an MTBF of 350 hours; if the two repairs took 6 hours in total, its MTTR is 3 hours.