Free tool
MTBF and MTTR calculator
Enter planned time, number of failures and repair time to get MTBF, MTTR and availability step by step. Add other stops to compare the maintenance view with OEE availability.
Result
What MTBF and MTTR tell you
MTBF (Mean Time Between Failures) is how long a machine runs on average between failures; MTTR (Mean Time To Repair) is how long it takes on average to get it back into production. The calculator starts with the example from our MTBF and MTTR guide: 600 planned hours, 5 failures and 10 hours of repair in total. The result is an MTBF of 118 hours, an MTTR of 2 hours and 98.3% availability. Adding 20 hours of changeovers and 8 hours of waiting for material brings OEE availability down to 93.7%. In the maintenance view, changeovers and other stops are not failures and count as uptime, so they do not change MTBF.
Excel template
To log failures line by line and get MTBF and MTTR per machine automatically, download the failure log and MTBF/MTTR template (Excel). All tools and templates are on the tools page.
Automating the failure log
Manual failure logs usually miss short failures and round start and end times. When the machine's stop signal comes from the PLC, every failure is recorded to the second and maintenance only picks the reason. See our downtime tracking and predictive maintenance pages.
Frequently asked questions
Common questions
How is MTBF calculated?
MTBF = total uptime / number of failures. Uptime is planned production time minus the time spent repairing failures. With 600 planned hours, 10 hours of repair and 5 failures, MTBF = 590 / 5 = 118 hours.
How is MTTR calculated?
MTTR = total repair time / number of repairs. Decide in advance whether repair time runs from the start of the failure until the machine is back in production; otherwise different shifts will get different results.
How do you calculate availability from MTBF and MTTR?
Availability = MTBF / (MTBF + MTTR). This counts failures only. Availability in OEE also counts changeovers, set-up and waiting for material, every stop not taken out of planned time (even a scheduled changeover), so it is usually lower.
Why do I get two different availability figures?
The maintenance view counts failures only; the production view (OEE availability) counts all stops. Both are right for their scope and should come from the same downtime records.
Is my data stored?
No. The calculation runs entirely in your browser and nothing is sent to a server.
Next step
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