MTBF Calculator

Calculate Mean Time Between Failures from total operating time and the number of failures, shown in hours, days and years. Calculates in your browser.

Mean time between failures

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In days-
In years-

Show the math

MTBF is the average uptime between failures of a repairable system:

MTBF = total operating time ÷ number of failures

Use the time the system was actually running. A higher MTBF means a more reliable system. MTBF describes repairable equipment; for parts that are replaced rather than repaired, use MTTF instead. Calculated entirely in your browser.

What this does

An MTBF calculator finds the Mean Time Between Failures — the average operating time between failures of a repairable system.

How to use it

  1. Enter the total operating time.
  2. Enter the number of failures.
  3. Read MTBF in hours, days and years.

How it works

A higher MTBF means greater reliability. Use MTBF for systems that are repaired and MTTF for items that are replaced.

MTBF = total operating time ÷ number of failures

Understanding your result

A higher MTBF means a more reliable system, but it is an average across many hours, not a guaranteed lifespan, so a unit can still fail tomorrow. Use it to compare designs and plan spares, not to predict a single device. MTBF applies to repairable systems; for parts you replace rather than fix, MTTF is the right measure.

Example

8,760 hours with 4 failures gives an MTBF of 2,190 hours.

Sources & methodology

Last updated .

Frequently asked questions

What is MTBF?

Mean Time Between Failures is the average operating time between failures of a repairable system. A higher MTBF indicates greater reliability.

How is it calculated?

Divide the total time the system was running by the number of failures during that time. For example, 8,760 hours with 4 failures gives an MTBF of 2,190 hours.

MTBF or MTTF?

Use MTBF for systems that are repaired and returned to service, and MTTF for items that are replaced rather than repaired.