MTBF Calculator — Mean Time Between Failures

MTBF = total operating time ÷ number of failures over that time. It’s the average time a machine runs between one unplanned breakdown and the next — a measure of how often problems happen, not how long they take to fix. Higher MTBF is better.

Operating time is planned production time minus downtime, not calendar time. Only unplanned breakdowns count as failures; scheduled PM stops and changeovers don’t.

MTBF and MTTR together give Availability = MTBF ÷ (MTBF + MTTR). MTBF usually moves more slowly than MTTR, because raising it means removing the root causes of failure — better PM, better lubrication, fixing repeat faults — rather than repairing faster.

This calculator is for one machine over one period, entered by hand. MachDatum CMMS calculates MTBF per asset from your breakdown work orders, so it updates as work orders close instead of waiting for a month-end tally.