Cloud & Networking

MTBF and Availability Calculator

Combine MTBF and MTTR to find steady-state availability.

By TheCalcTools Updated Formula checked and tested

Your numbers

Your results

Availability
Availability
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Expected failures per year
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Expected downtime per year (hours)
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MTBF and Availability Calculator by TheCalcTools

How the MTBF and Availability Calculator works

Enter the mean time between failures and the mean time to repair, both in hours.

Availability is the share of each failure-and-repair cycle during which the system works.

Failures per year is the hours in a year divided by the cycle length.

The formula

Availability = MTBF ÷ (MTBF + MTTR)

Worked example

Using the default values shown in the calculator:

MTBF (hours)8760
MTTR (hours)4
  1. Cycle length = 8,760 + 4 = 8,764 hours.
  2. Availability = 8,760 ÷ 8,764 = 99.9544%.
  3. Expected downtime per year ≈ 4.00 hours.

Result:

Availability99.9544
Expected failures per year1.00
Expected downtime per year (hours)4.00

Frequently asked questions

What is the difference between MTBF and MTTR?

MTBF is the average operating time between failures. MTTR is the average time to restore service after a failure.

How can I improve availability?

Either make failures rarer (higher MTBF) or recover faster (lower MTTR). Automation often cuts MTTR cheaply.

Sources and further reading

SLA Uptime and Downtime CalculatorSee how much downtime a given SLA actually allows Composite SLA Calculator (Serial and Parallel)Combine the availability of up to three components to see the overall result SLO Error Budget Calculator (Downtime and Burn Rate)Enter the SLO, the window and your traffic and errors so far

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This calculator gives estimates for information only. Check important results independently before you rely on them. See our disclaimer.