MTTR vs MTBF
MTBF (mean time between failures) measures how often an asset fails; MTTR (mean time to repair) measures how long it takes to fix. MTBF tracks reliability, MTTR tracks maintainability. Raising MTBF and lowering MTTR both cut downtime, and together they set an asset’s availability.
MTBF and MTTR are the two headline metrics for equipment reliability, and they answer different questions. MTBF (mean time between failures) is how long an asset runs, on average, before it fails again - a measure of reliability. MTTR (mean time to repair) is how long it takes, on average, to get a failed asset running again - a measure of maintainability. MTBF is total operating time divided by the number of failures; MTTR is total repair time divided by the number of repairs. You want MTBF high and MTTR low, and the two combine into availability, the share of time an asset is ready to work: Availability = MTBF / (MTBF + MTTR).
| Metric | Full name | What it measures | Formula | Better when | Improve by |
|---|---|---|---|---|---|
| MTBF | Mean time between failures | Reliability - how often it fails | Total uptime / number of failures | Higher | Root-cause fixes, preventive maintenance, better parts |
| MTTR | Mean time to repair | Maintainability - how fast you recover | Total repair time / number of repairs | Lower | Spares on hand, trained techs, clear procedures |
MTBF measures how often an asset fails; MTTR measures how quickly you recover. Availability = MTBF / (MTBF + MTTR).
Why it matters
Chasing one metric in isolation hides the real picture. An asset with a long MTBF can still wreck a schedule if every failure takes a day to repair (high MTTR), and a fast repair time means little if the asset fails every week (low MTBF). Availability, which both metrics feed, is what operations actually feel. For Australian operators running plant, fleet or field equipment, tracking both tells you where to spend: a low MTBF points to a reliability problem (design, parts, or maintenance intervals), while a high MTTR points to a response problem (spares, access, or technician availability). A worked example: an excavator that runs 400 hours between failures and takes 8 hours to repair has an availability of 400 / (400 + 8), or about 98 per cent.
How MapTrack helps
MapTrack records every failure, work order and repair against the asset, with timestamps for when a fault was raised and when it was closed out. Because that history is captured as work happens rather than reconstructed from memory, MTBF and MTTR can be calculated per asset, per site or per category without a separate spreadsheet, so you can see which assets are dragging availability down and why.
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Frequently asked questions
What is the difference between MTTR and MTBF?
MTBF (mean time between failures) measures reliability - how long an asset runs before it fails. MTTR (mean time to repair) measures maintainability - how long it takes to fix a failure. MTBF is total operating time divided by the number of failures; MTTR is total repair time divided by the number of repairs. In short, MTBF is about how often things break and MTTR is about how fast you fix them.
How do MTBF and MTTR affect availability?
Availability is the proportion of time an asset is ready to work, calculated as Availability = MTBF / (MTBF + MTTR). Raising MTBF (fewer failures) or lowering MTTR (faster repairs) both increase availability. For example, an asset with an MTBF of 400 hours and an MTTR of 8 hours has an availability of 400 / 408, or about 98 per cent.
What is a good MTBF or MTTR?
There is no universal target - a good MTBF and MTTR depend on the asset type, its duty cycle and how critical it is. The useful benchmark is your own trend over time: a rising MTBF and a falling MTTR mean your maintenance programme is working. Compare like assets against each other rather than against an external number.
How do you calculate MTBF and MTTR?
MTBF is total operating (uptime) hours divided by the number of failures over the same period. MTTR is total repair hours divided by the number of repairs. For instance, if a pump runs 1,000 hours and fails 5 times, MTBF is 200 hours; if those 5 repairs took 10 hours in total, MTTR is 2 hours.
Related terms
Mean Time Between Failures (MTBF)
Mean Time Between Failures (MTBF) is a reliability metric that measures the average elapsed time between inherent failures of a repairable system during normal operation. It is calculated by dividing the total operational time by the number of failures over a given period. MTBF is typically expressed in hours and is used to compare the reliability of assets, components, or equipment models.
Mean Time to Repair (MTTR)
Mean Time to Repair (MTTR) measures the average time required to diagnose and fix a failed asset and return it to operational status. It includes diagnosis, sourcing parts, performing the repair, and testing. MTTR is typically calculated by dividing the total repair time across all failures by the number of failure events in a given period.
Preventive Maintenance
Preventive maintenance (PM) is a proactive maintenance strategy in which assets are serviced at predetermined time or usage intervals to reduce the likelihood of failure. Tasks may include inspections, lubrication, filter changes, calibrations, and component replacements. PM schedules are typically based on manufacturer recommendations, regulatory requirements, or historical failure data.
Run-to-Failure Maintenance
Run-to-failure (RTF) is a deliberate maintenance strategy in which an asset is operated until it fails, at which point corrective maintenance is performed or the asset is replaced. It is a legitimate approach for non-critical, low-cost, or easily replaceable items where the cost of preventive maintenance exceeds the cost of failure. RTF should not be confused with neglect; it is an intentional decision based on risk and cost analysis.
Equipment Utilisation
Equipment utilisation measures the extent to which available equipment is being productively used, typically expressed as a percentage of available time or capacity. It is calculated by dividing actual usage time (or output) by total available time (or maximum capacity). Utilisation data can come from meter readings, operator logs, GPS tracking, or telematics systems. It is a key operational efficiency metric in asset-intensive industries.
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