Maintenance KPIs Explained: MTBF, MTTR and More
MTBF (mean time between failures) is the average operating time between one failure and the next, calculated as total operating time divided by the number of failures. MTTR (mean time to repair) is the average time needed to restore equipment after a failure, calculated as total repair time divided by the number of repairs. Higher MTBF and lower MTTR mean more available equipment.
Core maintenance KPIs and formulas
| KPI | What it measures | Basic formula |
|---|---|---|
| MTBF | Reliability of an asset | Total operating time ÷ number of failures |
| MTTR | Speed of repair | Total repair time ÷ number of repairs |
| Availability (uptime %) | Share of time the asset can operate | MTBF ÷ (MTBF + MTTR) × 100 |
| Downtime (max, min, average) | How long equipment is out of operation | Sum or average of out-of-service periods |
| PM compliance | Discipline of the preventive program | PM jobs completed on time ÷ PM jobs due × 100 |
| Maintenance vs equipment cost | Whether an asset is still worth maintaining | Maintenance cost ÷ equipment cost × 100 |
| Failures per equipment | Problem assets | Count of failures per asset over a period |
| Manpower load | Workload balance | Maintenance tasks or hours per technician |
What is MTBF?
Mean time between failures (MTBF) is the average time a repairable asset operates between one failure and the next. Formula: MTBF = total operating time ÷ number of failures. MTBF applies to repairable equipment; for parts that are replaced rather than repaired, mean time to failure (MTTF) is normally used instead.
What is MTTR?
Mean time to repair (MTTR) is the average time needed to restore an asset to working order after a failure. Formula: MTTR = total repair time ÷ number of repairs. State clearly what repair time includes, for example diagnosis, waiting for spare parts and testing, so that MTTR can be compared fairly between sites and teams.
How MTBF and MTTR determine availability
Availability combines both KPIs: availability = MTBF ÷ (MTBF + MTTR). Raising MTBF through better preventive maintenance, or lowering MTTR through faster response and spare-parts readiness, both increase the share of time an asset can operate. Tracking both on work orders makes the figures reliable, because every failure and repair is recorded with its times.
Worked example
A pump runs 1,000 hours in a quarter and fails 4 times. Its MTBF is 1,000 ÷ 4 = 250 hours. If the four repairs took 10 hours in total, MTTR is 10 ÷ 4 = 2.5 hours, and availability is 250 ÷ (250 + 2.5) ≈ 99.0%.
MTBF vs MTTR: key differences
| MTBF | MTTR | |
|---|---|---|
| Question it answers | How often does the asset fail? | How quickly is it repaired? |
| Better when | Higher | Lower |
| Mainly driven by | Asset design, operating conditions and preventive maintenance | Response time, skills, spare parts and approvals |
| Unit | Hours of operation | Hours of repair |
How to improve MTBF and reduce MTTR
To raise MTBF:
- Apply preventive maintenance to critical assets.
- Analyze repeat failures and fix their root causes.
- Make sure equipment is operated correctly and users are trained.
To lower MTTR:
- Require clear work requests that name the asset and location.
- Use priorities and tolerance periods so critical faults are handled first.
- Keep critical spare parts in stock.
- Give technicians mobile access to asset history.
Common calculation mistakes
- Counting planned preventive downtime as failures.
- Using different definitions of repair time at different sites.
- Comparing MTBF across unrelated asset types.
- Drawing conclusions from very few failures.
How to use these KPIs
- Rank assets by failures and downtime to decide where preventive maintenance should focus.
- Watch MTTR to find delays in spare parts, skills or approvals.
- Compare maintenance cost with equipment cost to support repair-or-replace decisions.
- Benchmark sites, teams and service providers using the same definitions.
Maintenance KPIs in Steady OMS
Steady OMS dashboards include maximum, minimum and average downtime, the PM performance meter, the maintenance event log, MTBF, manpower load, maintenance versus equipment cost, average time between failures, average time to repair and uptime %, and downtime versus throughput. Steady OMS provides more than 75 KPIs in total, on dashboards that each user can configure.
Frequently asked questions
There is no universal value. MTBF depends on the asset type, operating conditions and how failures are defined, so it is most useful for tracking the same asset or asset class over time.
Downtime is the total time equipment is unavailable. MTTR is the average repair time per failure and is one of the factors that make up downtime.
Generally yes, because it means fewer failures for the same operating time. Compare it only for the same asset or asset class, measured with the same failure definition.
MTBF applies to repairable assets and measures the time between failures. MTTF (mean time to failure) applies to items that are replaced rather than repaired and measures their average life until failure.
Talk to Steady Solutions
Tell us about your sites, assets and processes, and our team will show you how Steady OMS fits your organization. You can also contact us directly or call +966 55 353 3314.