MTBF Calculator
Enter operating hours and failure count. We'll calculate Mean Time Between Failures, failure rate, availability, and the probability your asset survives the next run — instantly, in the browser. Nothing leaves your device.
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Mean Time Between Failures
Average operating hours between unplanned breakdowns. Higher is better — it's the headline reliability number for any repairable asset.
Failure rate (λ)
The flip side of MTBF: how often the asset fails per hour of running. Multiply by 1,000 for a number humans can read.
Reliability R(t)
The probability the asset runs for a given window without failing, assuming a constant failure rate. At t = MTBF, odds are only ~37% — MTBF is an average, not a guarantee.
How to calculate MTBF — worked example
A pump ran for 4,180 hours over six months and broke down 5 times. MTBF = 4,180 ÷ 5 = 836 hours — on average, one failure roughly every 5 weeks of running. Count only unplanned failures, and only actual running hours: including planned services or idle time quietly inflates the number.
Want the full method, the mistakes that wreck the number, and MTBF vs MTTF explained? Read the MTBF calculation guide — or calculate repair-side metrics with the MTTR calculator.
Stop calculating. Start measuring.
AssetOS logs runtime and failures against every asset as work happens — so MTBF, MTTR, and reliability trends are a live report, not a monthly spreadsheet rebuild.
MTBF · FAQ
How do you calculate MTBF?+
Divide total operating hours by the number of unplanned failures in the same period. Example: 4,180 running hours with 5 breakdowns gives an MTBF of 836 hours. Use actual running time, not calendar time, and count only unplanned failures — planned maintenance stops don't belong in the number.
What is the MTBF formula?+
MTBF = Total operating time ÷ Number of failures. Its reciprocal is the failure rate (λ = failures ÷ operating time), and together with MTTR it gives availability: Availability = MTBF ÷ (MTBF + MTTR).
What is the difference between MTBF and MTTF?+
MTBF applies to repairable assets — pumps, vehicles, HVAC — and measures time between failures. MTTF (Mean Time To Failure) applies to non-repairable items like bulbs, bearings, or fuses that get replaced rather than fixed, and measures average life until the single failure.
How do you calculate reliability from MTBF?+
Use R(t) = e^(−t ÷ MTBF), which gives the probability of running for time t without failure assuming a constant failure rate. Note that at t = MTBF the survival probability is only about 37% — MTBF is an average, not a guaranteed failure-free window.
What is a good MTBF?+
There is no universal benchmark — a good MTBF for a conveyor differs from one for a delivery van. What matters is the trend per asset: calculate MTBF for each critical asset, track it month over month, and prioritise the assets where a falling MTBF meets high downtime cost.
Does MTBF include planned downtime?+
No. MTBF only counts unplanned failures, and the operating-hours input should exclude every stop — planned or unplanned. Mixing planned services into the failure count (or idle time into the hours) is the most common way teams quietly wreck the metric.