Most maintenance teams track the metrics that are easiest to count: number of work orders completed, number of PMs done, hours billed. These numbers tell you about activity. They tell you almost nothing about performance.
The difference between a reactive maintenance operation and a high-performing one isn't the quantity of work—it's knowing which numbers actually predict whether your equipment will fail next month.
Here are the eight metrics that matter. Not all of them are easy to calculate. The ones that aren't easy are usually the most important.
MTBF: Mean Time Between Failures
MTBF tells you how often a specific piece of equipment fails. Calculate it by dividing total uptime hours by the number of failures in a given period.
If your packaging line ran for 4,200 hours last year and failed 7 times, MTBF is 600 hours. That number tells you two things: where to set your PM interval (somewhere below 600 hours), and whether your maintenance program is improving over time. If MTBF climbs from 600 to 750 hours year-over-year, your preventive maintenance is working. If it drops, something changed—and you need to find out what.
Track MTBF at the individual asset level, not just the facility average. A facility average MTBF of 400 hours might be hiding two assets failing every 50 hours and eight that almost never fail. The average is meaningless. The outliers are where your money is going.
MTTR: Mean Time to Repair
MTTR measures how long it takes to restore equipment after a failure—from the moment the failure is detected to the moment the asset is back in service. Calculate it by dividing total repair time by number of repairs.
High MTTR usually points to one of three problems: technicians can't find spare parts, the failure diagnosis process is slow, or the repair procedures aren't documented and technicians are figuring it out from scratch each time.
The target MTTR varies dramatically by industry and asset type. A hospital's target for a ventilator support system might be under 30 minutes. A manufacturing line's target for a conveyor motor might be 4 hours. What matters is your trend: is MTTR improving, stable, or getting worse?
CMMS software like Limble CMMS and UpKeep calculate MTTR automatically from work order data. If you're calculating it manually, you're probably not calculating it often enough to catch problems early.
Planned Maintenance Ratio
This is the ratio of planned maintenance hours to total maintenance hours. If your team spent 200 hours on planned PMs and 200 hours on emergency repairs last month, your PMR is 50%.
World-class maintenance operations run at 80-90% planned maintenance. Below 60% means you're in reactive mode—spending most of your time fighting fires rather than preventing them. The cost difference is significant: emergency repairs typically cost 3-5x more than planned maintenance for the same failure, when you factor in overtime, expedited parts, and production downtime.
PMR is also the best single leading indicator of where your maintenance program is headed. When PMR starts to drop month-over-month, it's an early warning that your PM program is slipping before the equipment failures start to accumulate.
Overall Equipment Effectiveness (OEE)
OEE is the gold standard KPI for manufacturing environments. It measures three things simultaneously: availability (was the equipment running when it was supposed to?), performance (when it was running, was it running at full speed?), and quality (were the outputs defect-free?).
Multiply those three percentages together and you get OEE. A machine with 90% availability, 95% performance, and 98% quality has an OEE of 83.8%—which is considered world-class. Most manufacturers start at 40-60% OEE and consider anything above 85% excellent.
Maintenance directly controls the availability component of OEE. Every hour of unplanned downtime reduces availability. Every PM completed on schedule that prevents a failure preserves it. If your leadership team is focused on OEE, connecting maintenance KPIs to the availability component makes the ROI of your maintenance program visible in financial terms.
PM Compliance Rate
PM compliance is the percentage of scheduled preventive maintenance tasks completed on time. It's the most direct measure of whether your PM program is actually being executed.
Calculate it monthly: divide PMs completed on or before their due date by total PMs scheduled. A rate above 90% is excellent. Between 70-90% is functional but has room for improvement. Below 70% signals that your PM schedule is aspirational rather than operational.
When PM compliance is low, the causes are almost always one of three things: technicians have too many corrective work orders competing for the same time, the PM tasks themselves are taking longer than the schedule assumes, or the CMMS isn't generating proper reminders and escalations. Each cause has a different fix.
Maintenance Cost as a Percentage of Asset Replacement Value
This metric—sometimes called the Maintenance Cost Ratio—tells you whether you're spending appropriately on maintaining your assets. Industry benchmarks suggest healthy operations spend 2-4% of asset replacement value on maintenance annually.
Spending below 2% often means deferred maintenance is accumulating: you're spending less now but setting up expensive failures later. Spending above 5% suggests either over-maintenance (too many PMs for the failure risk) or an aging asset base that needs capital investment rather than maintenance dollars.
To calculate it: total maintenance spending for the year divided by current replacement cost of all maintained assets. This metric is most useful when tracked over 3-5 years to spot trends, not as a single-year snapshot.
Work Order Backlog
Your work order backlog is the number of open work orders at any given time. Specifically, the maintenance hours required to complete them. A backlog of 200 work orders sounds alarming. A backlog representing 40 hours of maintenance work for a 5-person team is actually healthy.
The danger signal is a growing backlog. If your backlog grows by 10% each month, your team's capacity to complete work is falling behind the rate at which new work is being created. That gap compounds—and eventually you're running 100% reactive, putting out fires while the PM schedule becomes fiction.
Track backlog in hours, not work order count. And track it by priority tier. An aging backlog of low-priority work is fine. An aging backlog of high-priority or safety-related work orders is a liability.
Wrench Time
Wrench time is the percentage of a maintenance technician's shift actually spent on hands-on repair and maintenance work—as opposed to traveling between jobs, waiting for parts, searching for documentation, or administrative tasks.
Industry studies consistently show that most technicians spend only 25-35% of their shift on actual maintenance work. The rest is consumed by everything else. World-class operations get wrench time above 50%.
Improving wrench time is not about pushing technicians harder. It's about removing friction: stocking parts closer to the equipment, ensuring work orders include clear task descriptions and documentation links, routing work orders digitally rather than on paper, and eliminating unnecessary approval steps.