# Machine Availability Guarantee Calculator from MTBF and MTTR

> Source: https://netray.co/tools/machine-availability-guarantee-mtbf-mttr-calculator
> Publisher: Netray (netray.co), AI and integration engineering for ERP and manufacturing systems.
> Section: Free Tools

## Short answer

Compute inherent and operational availability from MTBF, MTTR, parts wait and planned maintenance, and compare it with a contractual guarantee.

## Category

maintenance

## Industry

Industrial Machinery

## Audience

- Service engineer
- Reliability engineer
- OEM contracts manager

## Tool

**Kind:** calculator

**Currency:** $

**Inputs:**

#### Mean time between failures (MTBF)

**Key:** mtbf

**Type:** number

**Default:** 450

**Min:** 1

**Step:** 10

**Unit:** hours

#### Mean time to repair (MTTR), hands-on

**Key:** mttr

**Type:** slider

**Default:** 4

**Min:** 0.5

**Max:** 48

**Step:** 0.5

**Unit:** hours

#### Logistics delay per failure (technician arrival, parts wait)

**Key:** ldt

**Type:** number

**Default:** 6

**Min:** 0

**Step:** 0.5

**Unit:** hours

#### Scheduled operating hours per year

**Key:** sched

**Type:** number

**Default:** 6000

**Min:** 1

**Step:** 100

**Unit:** hours

#### Planned preventive maintenance per year

**Key:** pm

**Type:** number

**Default:** 80

**Min:** 0

**Step:** 5

**Unit:** hours

#### Contractual availability guarantee

**Key:** guarantee

**Type:** number

**Default:** 95

**Min:** 50

**Max:** 99.9

**Step:** 0.5

**Unit:** %

#### Penalty per hour below guarantee

**Key:** penalty

**Type:** number

**Default:** 400

**Min:** 0

**Step:** 50

**Unit:** $ per hour

**Outputs:**

#### Inherent availability (MTBF / (MTBF + MTTR))

**Key:** inherent

**Expr:** mtbf / (mtbf + mttr) * 100

**Format:** percent

#### Operational availability including logistics delay

**Key:** operational

**Expr:** mtbf / (mtbf + mttr + ldt) * 100

**Format:** percent

#### Expected failures per year

**Key:** failures

**Expr:** sched / (mtbf + mttr + ldt)

**Format:** decimal

#### Total downtime per year

**Key:** down

**Expr:** failures * (mttr + ldt) + pm

**Format:** hours

#### Availability including planned maintenance

**Key:** achieved

**Expr:** max(0, (sched - down) / sched * 100)

**Format:** percent

**Primary:** true

#### Hours short of the guarantee per year

**Key:** gap_hours

**Expr:** max(0, down - sched * (1 - guarantee / 100))

**Format:** hours

**Primary:** true

#### Annual penalty exposure

**Key:** exposure

**Expr:** gap_hours * penalty

**Format:** currency

#### Maximum hands-on MTTR plus delay that meets the guarantee, before PM

**Key:** max_repair

**Expr:** mtbf * (1 - guarantee / 100) / (guarantee / 100)

**Format:** hours

**Chart:**

#### Availability vs MTTR

**Type:** line

**X:** mttr

**From:** 0.5

**To:** 48

**Steps:** 24

**Series:**

- operational
- achieved

**Disclaimer:** Steady-state model with constant failure and repair rates. Check how your contract defines availability, exclusions and measurement period.

## Content

**Intro:** Availability guarantees turn reliability into money. This calculator shows whether your MTBF, repair time and spare parts logistics can meet the percentage in the contract, and what shortfall hours would cost.

**Sections:**

#### How to use it

**Body:** Enter the MTBF from field data or a reliability prediction, the hands-on repair time, and the logistics delay that includes technician travel and waiting for parts. Add scheduled operating hours per year, planned preventive maintenance and the guarantee in the contract, plus any penalty per hour. The results give inherent availability, operational availability with logistics delay, expected failures, total downtime, availability including planned maintenance, and the number of hours short of the guarantee. The last output tells you the maximum total repair plus delay time that would still meet the guarantee for a given MTBF.

#### The formulas

**Body:** Inherent availability is MTBF divided by MTBF plus MTTR and ignores logistics and preventive work. Operational availability adds the logistics delay to the denominator. Failures per year are scheduled hours divided by one operating cycle, meaning time to failure plus the repair and delay. Downtime is failures times repair and delay, plus planned maintenance. Achieved availability is scheduled hours less downtime divided by scheduled hours. The maximum repair time equals MTBF times (1 - g) divided by g, where g is the guarantee as a fraction. Definitions differ between contracts, so mirror yours.

**Bullets:**

- Is planned maintenance excluded from the measurement?
- Are customer-caused stops excluded?
- Is travel time counted from the call or from the arrival?

#### Reading the chart

**Body:** Availability falls quickly once repair time gets long relative to MTBF. For a 450 hour MTBF, a 4 hour repair plus 6 hours of delay gives about 97.8 percent operational availability, but planned maintenance and the repair tail bring the annual figure lower. The chart shows that shortening the logistics delay, through local spares, remote diagnostics or a technician in the region, often improves the result more than improving the MTBF a few percent. Use it to decide whether a guarantee is realistic and what service set-up it requires.

#### Common mistakes

**Body:** The most common error is using design MTBF from component data and ignoring field issues such as operator-induced stops and wear-out. Another is promising a percentage without defining the measurement window and exclusions. Finally, many contracts count only unplanned downtime, which makes preventive work free; others count everything. If your ERP service orders have start, arrival and completion timestamps per machine serial number, you can calculate real MTBF and MTTR rather than estimating them.

**Cta:** We can build a read-only agent that calculates MTBF, MTTR and logistics delay from your service order history per machine model.

**Faq:**

#### What is the difference between inherent and operational availability?

**Answer:** Inherent availability counts only the active repair time and reflects design. Operational availability includes real-world delays such as waiting for a technician or part, so it is always lower. Contracts that measure actual uptime behave like operational availability.

#### How do I get MTBF for a new machine?

**Answer:** Start with a prediction from component failure rates or data from a similar earlier model, and then replace it with field data as machines accumulate hours. Early values are uncertain, so leave a margin before offering a guarantee.

#### Does 95 percent availability mean much downtime?

**Answer:** On 6000 scheduled hours, 95 percent allows 300 hours of downtime per year. That sounds large, but unplanned stops, preventive maintenance and waiting time all consume it. Many users expect 98 percent or better on critical machines.

#### Is the constant failure rate assumption realistic?

**Answer:** It is a simplification that fits the useful-life period of many assemblies. Early-life and wear-out phases have different failure behavior. For long guarantees on aging machines, use a more detailed reliability model.

## Search terms

availability calculator MTBF MTTR, inherent availability formula, operational availability calculator, uptime guarantee machine, availability guarantee contract, MTBF MTTR availability, equipment availability percentage, service level availability OEM

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