# MTBF, MTTR and Availability Calculator from SAP PM Breakdown Data

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

## Short answer

Feed in operating hours, failure count and breakdown hours from SAP PM notifications. Get MTBF, MTTR, inherent availability and reliability over a mission time.

## Category

sap

## Erp

SAP PM

## Industry

Manufacturing

## Audience

- Reliability engineer
- SAP PM consultant
- Maintenance manager

## Tool

**Kind:** calculator

**Inputs:**

#### Total calendar hours in period

**Key:** period_hours

**Type:** number

**Default:** 8760

**Min:** 1

**Step:** 100

**Unit:** hours

**Help:** For one year use 8,760. For a machine that runs 2 shifts, use scheduled operating hours instead if you want operational availability.

#### Number of failures

**Key:** failures

**Type:** number

**Default:** 14

**Min:** 1

**Step:** 1

**Unit:** events

**Help:** Count of breakdown notifications (malfunction reports) in the period for the equipment or class.

#### Total breakdown (repair) hours

**Key:** downtime

**Type:** number

**Default:** 96

**Min:** 0

**Step:** 1

**Unit:** hours

**Help:** Sum of the breakdown duration on those notifications.

#### Mission time

**Key:** mission

**Type:** number

**Default:** 168

**Min:** 1

**Step:** 8

**Unit:** hours

**Help:** Run length you want to survive without failure, such as one week.

**Outputs:**

#### Operating (up) hours

**Key:** uptime

**Expr:** max(0, period_hours - downtime)

**Format:** hours

#### MTBF

**Key:** mtbf

**Expr:** uptime / failures

**Format:** hours

**Primary:** true

**Description:** Mean time between failures: operating hours divided by failures.

#### MTTR

**Key:** mttr

**Expr:** downtime / failures

**Format:** hours

**Primary:** true

**Description:** Mean time to repair: downtime hours divided by failures.

#### Inherent availability

**Key:** avail

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

**Format:** percent

#### Failure rate per 1,000 hours

**Key:** rate

**Expr:** failures / uptime * 1000

**Format:** decimal

#### Reliability over mission time

**Key:** reliab

**Expr:** exp(0 - mission / mtbf) * 100

**Format:** percent

**Description:** Probability of running the mission time without failure, assuming a constant failure rate (exponential model).

**Chart:**

#### Availability vs number of failures

**Type:** line

**X:** failures

**From:** 1

**To:** 60

**Steps:** 30

**Series:**

- avail

**Disclaimer:** Assumes a constant failure rate. Wear-out failures follow other distributions, such as Weibull, and need separate analysis.

## Content

**Intro:** MTBF, MTTR and availability are the three numbers every reliability review asks for. This calculator derives them from the failure counts and breakdown hours you can pull from SAP PM malfunction notifications.

**Sections:**

#### How to use it

**Body:** Pull malfunction (breakdown) notifications for a piece of equipment, class or functional location from IW29 for the period. Count the failures and sum the breakdown duration recorded on each notification. Enter those with the period hours and a mission time. The tool returns MTBF, MTTR, availability, failure rate and the probability of surviving the mission.

**Bullets:**

- Use only true failures, not planned stops or minor adjustments.
- Exclude notifications with no breakdown indicator or duration.
- Group by equipment class to get enough events for a stable mean.

#### The formulas

**Body:** MTBF equals operating hours divided by the number of failures. MTTR equals total repair hours divided by failures. Inherent availability equals MTBF divided by MTBF plus MTTR. Reliability for a mission of t hours under a constant failure rate is e to the power of minus t over MTBF. The chart shows how availability falls as the failure count rises while the average repair stays equal.

#### Reading results and pitfalls

**Body:** With fewer than about five failures MTBF is too noisy to trust. A falling MTTR with a flat MTBF means you are repairing faster, not preventing failures. Check data quality first: if technicians leave breakdown start and end blank, MTTR will be understated. Breakdown duration in SAP is an entered field, not computed from order times.

**Bullets:**

- Do not compare MTBF between assets with different duty cycles.
- A high MTTR points to spares, skills or access, not reliability.
- Use failure codes (damage and cause) to find the repeat offender.

**Cta:** If you want MTBF and MTTR tables updated automatically from your notification history, Netray can build a read-only report for you inside your own environment.

**Faq:**

#### How do I get MTBF from SAP PM?

**Answer:** Count malfunction notifications with a breakdown indicator for the equipment and period, then divide operating hours by that count. SAP also offers breakdown statistics in the plant maintenance information system, but results depend on data quality.

#### What is the difference between MTBF and MTTF?

**Answer:** MTBF applies to repairable items and counts time between failures, while MTTF applies to non-repairable items and measures time to the first failure. For most plant equipment you use MTBF.

#### Is availability the same as uptime percentage?

**Answer:** Inherent availability uses only failures and repairs. Operational availability also counts planned downtime, waiting and logistics time. Enter scheduled operating hours and include all downtime to approximate operational availability.

#### Why is reliability shown as exponential?

**Answer:** The exponential model is the standard first approximation when failures are random. It does not suit wear-out failures such as bearings near end of life, where a Weibull analysis fits better.

## Search terms

mtbf mttr calculator, availability calculator maintenance, sap pm mtbf mttr, mean time between failures formula, mean time to repair calculation, inherent availability formula, breakdown duration notification sap, failure rate per 1000 hours

---
Talk to an engineer: https://netray.co/contact?intent=erp_ai | Machine catalog: https://netray.co/agent/catalog.json