Availability Calculator

Work out inherent availability from MTBF and MTTR, shown as a percentage with the downtime it implies per year and month. Calculates in your browser.

Availability

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Downtime per year-
Downtime per month-

Show the math

Inherent availability is the fraction of time a system is up over a full repair cycle:

A = MTBF ÷ (MTBF + MTTR)

A longer mean time between failures or a shorter mean time to repair both raise availability. The result is shown as a percentage along with the downtime it implies over a year and a month. Calculated entirely in your browser.

What this does

An availability calculator works out inherent availability from MTBF and MTTR, as a percentage with the downtime it implies.

How to use it

  1. Enter the MTBF.
  2. Enter the MTTR.
  3. Read availability and implied downtime.

How it works

It is the share of time a system is up across a full failure-and-repair cycle. Raise MTBF or cut MTTR to improve it.

availability = MTBF ÷ (MTBF + MTTR)

Understanding your result

This is inherent availability across a full failure-and-repair cycle, so it captures only MTBF and MTTR, not maintenance windows, dependencies, or human delay, which is why real-world availability usually comes in lower. You raise it either by failing less often or recovering faster, and cutting MTTR is often the cheaper lever.

Example

An MTBF of 2,190 h with an MTTR of 3 h gives about 99.86% availability.

Sources & methodology

Last updated .

Frequently asked questions

How is availability calculated?

Availability is MTBF divided by the sum of MTBF and MTTR. It is the share of time the system is expected to be up across a full failure-and-repair cycle.

How can I improve it?

Either increase the mean time between failures or reduce the mean time to repair. Both raise the percentage and cut allowed downtime.

Is anything uploaded?

No. The calculation runs entirely in your browser.