MTTF Calculator

Calculate Mean Time To Failure for non-repairable items from total operating time and the number of units, shown in hours, days and years. Calculates in your browser.

Mean time to failure

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In days-
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Show the math

MTTF is the average lifespan of a non-repairable item, once it fails, it is replaced:

MTTF = total operating time ÷ number of units

Sum the running hours of every unit under test and divide by how many there were. Use MTTF for components such as drives or power supplies; use MTBF for systems that are repaired and kept in service. Calculated entirely in your browser.

What this does

An MTTF calculator finds the Mean Time To Failure — the average lifespan of a non-repairable item that is replaced rather than repaired.

How to use it

  1. Enter the total operating time across all units.
  2. Enter the number of units.
  3. Read MTTF in hours, days and years.

How it works

Once a non-repairable item fails it is replaced, which is common for drives and power supplies.

MTTF = total operating hours ÷ number of units

Understanding your result

This is the average lifespan of a part you replace rather than repair, like a drive or power supply, so treat it as a fleet expectation, not a warranty on any one unit. Use it to schedule proactive replacement before the failure rate climbs, since half of a population fails before the mean and half after.

Example

50,000 hours across 10 units gives an MTTF of 5,000 hours.

Sources & methodology

Last updated .

Frequently asked questions

What is MTTF?

Mean Time To Failure is the average lifespan of a non-repairable item, once it fails it is replaced rather than repaired. It is common for drives, power supplies and similar components.

How is it calculated?

Sum the operating hours of every unit tested and divide by the number of units. For example, 50,000 hours across 10 units gives an MTTF of 5,000 hours.

Is my data private?

Yes. Everything is calculated locally in your browser.