Maintenance Calculators
Failure Rate Calculator
Use this calculator when you want the rate of failures per hour or per day over a defined operating period.
Direct answer
Failure rate is calculated by dividing the number of failures by the total operating time.
Definition
Failure rate shows how often failures happened during the operating time being reviewed.
Formula
Failure Rate = Number of Failures / Total Operating Time
What it measures
It measures the frequency of failures per selected time unit.
Important limitation
Failure rate is only as useful as the failure definition behind it, and it should not be treated as exact proof of future failure timing.
How to calculate Failure Rate
Failure rate is calculated by dividing the number of failures by the total operating time.
Formula
Failure Rate = Number of Failures / Total Operating Time
Count the failures in the review period, total the operating time, and divide failures by time.
Explanation of every input
- Number of failures
- Enter the value for the same asset scope and time period used in the rest of the calculation.
- Total operating time
- Enter the value for the same asset scope and time period used in the rest of the calculation.
- Operating time unit
- Select the unit or option that matches the values you want to calculate with.
Worked example
- Failures6
- Operating time3,000 hours
6 / 3,000 = 0.002 failures per hour
The equipment failed at a rate of 0.002 failures per hour, or about one failure every 500 hours.
What the result means
Lower is generally preferable because failures are occurring less often.
Failure rate is a practical way to compare failure frequency when assets operate for different amounts of time.
It is closely related to MTBF when the underlying assumptions about failure behavior are appropriate.
Common interpretation mistakes
- Forcing a non-zero MTBF estimate when no failures were recorded in the period.
- Comparing failure rates between assets that operate under very different duty or environmental conditions.
- Including planned shutdown events as failures.
Practical ways to improve or use the metric
- Break failure rate down by failure mode so one chronic issue does not stay hidden in the total count.
- Review failure rate alongside PM completion and repeat work history.
- Separate operator resets, nuisance trips, and full maintenance failures if they trigger different follow-up actions.
Related calculators
MTBF Calculator
Calculate average operating time between failures for repairable equipment using operating time and failure count.
MTTR Calculator
Calculate average repair time per repair event using total repair downtime and the number of repairs.
Equipment Availability Calculator
Calculate scheduled-time availability, available time, and downtime percentage from required time and downtime.
Failure Rate FAQs
Practical questions maintenance teams often ask when reviewing this metric.
- Can failure rate be zero?
- Yes. If no failures were recorded in the period, the failure rate is zero for that period. That does not automatically mean the risk of failure is zero.
- Is failure rate the same as MTBF?
- No. Failure rate measures failures per unit of time. MTBF measures average time between failures. They are inverse-style measures only when the same assumptions fit the data.
- Should minor stops be counted as failures?
- Only if your plant defines them that way. The important thing is to use a consistent rule so the trend remains useful.
- Why is failure rate helpful for reliability review?
- It shows whether failures are happening more or less frequently over comparable operating time, which helps focus reliability work where repeat issues are strongest.
Stop calculating maintenance KPIs manually
MaintBoard connects work orders, preventive maintenance, downtime, labor, parts and asset history so maintenance metrics can be reviewed from actual maintenance records.