- Maintenance · CMMS
- Operations Manager, Plant / Operations Director, CFO / Finance, Quality / Audit
- Manufacturing, Logistics and warehousing
Maintenance KPIs: MTBF, MTTR and the few numbers worth tracking
In short
MTBF (mean time between failures) is the average operating time between breakdowns of a machine, and MTTR (mean time to repair) is the average time needed to restore it. Together they show how often a machine fails and how long it stays down. Both depend on recording each failure with start and end times against the specific machine. Start with four to six measures, review them monthly and use them to choose where to act. Remanently CMMS keeps the records these numbers come from.
Why measure at all
Maintenance produces a lot of activity and little visible result. A good month looks like nothing happening: machines run, nobody notices. Numbers make the effect visible. They show whether the planned work reduces stops, which machines absorb the most time and whether the team responds fast enough.
The danger is the opposite: dozens of indicators nobody reads. Pick a few, define them clearly and look at them on a fixed day each month. The rest of this page covers the main ones and how to compute them.
MTBF: mean time between failures
MTBF is the average operating time between one failure and the next. The formula is simple.
MTBF = total operating time divided by number of failures
An illustration with made-up numbers: a packaging machine runs 600 hours in a quarter and stops because of a fault 4 times. MTBF is 600 divided by 4, so 150 hours. If the next quarter shows 6 failures in the same 600 hours, MTBF falls to 100 hours, and the machine deserves attention.
Two cautions. First, count operating time, not calendar time, otherwise a machine that runs one shift looks more reliable than one that runs three. Second, agree what counts as a failure. A stop that needs a technician is a failure; a jam cleared by the operator in a minute may not be. Write the rule down.
MTTR: mean time to repair
MTTR = total repair time divided by number of repairs
With the same machine: four failures, with downtimes of 2, 5, 1 and 4 hours, give a total of 12 hours and an MTTR of 3 hours. MTTR tells you how long the machine stays out of service when it fails.
It hides several delays, so look at the parts: time from the report to the arrival of a technician, time to diagnose, time waiting for a part and time to repair. A high MTTR often comes from waiting, not from the work. If parts are the problem, see spare parts inventory management.
Other measures worth having
| Measure | What it shows | How to read it |
|---|---|---|
| Planned vs unplanned work share | How much time goes to scheduled tasks and how much to emergencies | Falling unplanned share suggests prevention is working |
| Schedule compliance | Share of planned tasks completed on time | Low numbers point to execution problems, not to the plan |
| Response time | Time from report to first action | Shows whether reports are seen and assigned |
| Completion time | Time from report to closed order | Includes waiting for parts and approvals |
| Repeat failures | Same machine, same fault within a period | Signals that a repair did not remove the cause |
| Maintenance cost per machine | Labor and parts spent per asset | Supports repair or replace decisions |
| Backlog | Open work orders and their age | A growing backlog means capacity is short or priorities unclear |
Downtime and availability are also common, but they depend on how you record stop and start times. Add them when that recording is reliable.
What you need in the records
None of these numbers is possible without disciplined records. For every failure you need the machine, the time of the stop, the time of the restart, the cause, the work done, the part used and who did it. If any of these are missing, the average is wrong or cannot be calculated.
That is the real reason to keep a machine log and to close every work order with real data. The indicator is only as good as the entry behind it.
How to start
- Choose four to six measures. Typically MTBF, MTTR, share of planned work, schedule compliance, repeat failures and backlog.
- Define each one in a sentence. What counts as a failure, when downtime starts and ends, which machines are covered.
- Begin with the critical machines. Averages across everything hide the problem machines.
- Review monthly, with the same people. Manager, team leader and a technician, thirty minutes.
- Act on one finding per meeting. One machine, one cause, one owner. Then check next month whether the number moved.
Misuse to avoid
Do not use the numbers to rank technicians. If the records are used mainly to blame, people will record less, and the data becomes worthless. Use them to understand machines and processes. Do not compare averages between very different machines. And remember that a short MTTR is not always good: a quick patch that fails again next week improves MTTR and worsens MTBF.
Roles
The maintenance manager uses MTBF and repeat failures to choose where to schedule work. The plant director watches unplanned stops and backlog. Finance watches cost per machine and asks whether the trend justifies the maintenance budget. Quality can use failure history when a machine problem might have affected output.
Reading a trend rather than a number
A single month of MTBF means little, because failures are irregular. Look at a rolling window of three to six months and compare it with the same machine earlier, not with other machines. When a number moves, ask what changed: a new operator, a different product, a part from another supplier, a skipped inspection. The number points at a question; the history of the machine usually holds the answer.
Where Remanently CMMS fits
Remanently CMMS records reports, work orders, statuses and completed work against the machine, and offers basic reporting in the FIRST plan and extended reporting from QUICK START. The TIME IS MONEY plan adds response and completion times, labor and repair costs, failure history analysis and maintenance dashboards. See CMMS pricing for plan scope and Remanently CMMS for the module. The overall guide is the CMMS software hub.
Frequently asked questions
What is MTBF?
Mean time between failures: total operating time divided by the number of failures. It shows how often a machine breaks down.
What is MTTR?
Mean time to repair: total repair time divided by the number of repairs. It shows how long a machine stays out of service when it fails.
How many KPIs should a small team track?
Four to six. Typical choices are MTBF, MTTR, share of planned work, schedule compliance, repeat failures and backlog.
What data do I need to calculate them?
For each failure: the machine, stop and restart times, cause, work done, part used and who did it. Missing entries make the averages unreliable.
Which Remanently CMMS plan includes response and completion times?
Response and completion times, labor and repair costs, failure history analysis and maintenance dashboards are part of the TIME IS MONEY plan.
Should KPIs be used to evaluate technicians?
That is not their best use. Data used mainly to blame leads to less recording. Use it to understand machines, parts and processes.
See your own failure data as numbers
Book a short demo and we will show how reports and work orders on your machines turn into MTBF, MTTR and repeat-failure views.