CMMS stands for computerised maintenance management system, and behind the acronym it is four things: a register of the assets you own, a schedule of what each one needs and when, the work orders raised against them, and the history of what was actually done. That is the whole definition, and it is worth being blunt about because the category is sold with a much longer list. Anything a product does beyond those four is an extra, and some of the extras belong to neighbouring categories entirely. This page sets out what a CMMS is, what it is not, and when a site is ready for one.
The four things, in the order they matter
The register comes first, because nothing else can exist without it. The schedule sits on the register. The work order records one job against one asset. The history is what the work orders accumulate into, and it is the only reason to keep the other three honest: without history, every interval is a guess nobody can check.
What a CMMS is not
It is not an EAM platform, which adds spare-parts inventory, purchasing, capital planning and multi-site rollups. It is not facilities management software, which manages buildings as a service rather than equipment. It is not a condition-monitoring system, which is sensors and analytics. Products blur these lines in their marketing and the distinction matters when you are comparing prices.
When a site is ready for one
When somebody other than the schedule's author needs to answer what is overdue. Below that, a spreadsheet genuinely works and this site would rather say so. The trigger is not asset count, it is the second person.
What it changes, honestly
It does not make anybody do maintenance better. It makes the register visible, the schedule staffable and the history retrievable, and those three things are what let a maintenance manager argue with evidence. On the worked example this site publishes, the argument is worth $111,283.20 a year in avoidable labour.
Questions people ask about what is cmms
Is CMMS the same as EAM?
No. EAM includes the CMMS functions and adds inventory, purchasing, capital planning and asset lifecycle costing. If you need those, buy EAM; if you do not, you are paying for configuration you will never turn on.
What does the C stand for?
Computerised, which dates the acronym to when the alternative was a card index. Both computerised and computerized spellings are used and mean the same thing.
Do we need a CMMS if we outsource maintenance?
You still need the register and the history, because they are yours and the contractor's records leave with the contractor. What changes is who raises the work orders.