# MTBF

**URL:** https://kaizumi.com/dictionary/mtbf

**Description:** MTBF (Mean Time Between Failures) measures average equipment reliability by calculating the average operating time between breakdowns.

**Category:** tpm

**Tags:** metrics, equipment, foundational

## Definition

MTBF (Mean Time Between Failures) is a reliability metric that measures the average time equipment operates between failures. It is calculated by dividing total operating time by the number of failures in that period. Higher MTBF indicates more reliable equipment. MTBF helps predict maintenance needs, compare equipment reliability, justify improvement investments, and track the effectiveness of TPM initiatives. Combined with MTTR (Mean Time To Repair), MTBF enables availability calculations.

## Examples

### Manufacturing

> A CNC machine operated 2,000 hours over six months with 4 breakdowns. MTBF = 2,000 / 4 = 500 hours. After implementing TPM, the next six months showed 2,000 hours with only 2 breakdowns. MTBF improved to 1,000 hours—double the reliability.

### Healthcare

> An infusion pump fleet averaged 8,000 hours of operation with 10 failures across the year. MTBF = 800 hours. After improving maintenance procedures and operator training, failures dropped to 5 per year—MTBF improved to 1,600 hours.

### Administrative

> A server averaged 8,760 hours uptime per year with 6 unplanned failures. MTBF = 1,460 hours. Hardware upgrades and improved cooling reduced failures to 2 per year, improving MTBF to 4,380 hours.

## Key Points

- MTBF = Total Operating Time / Number of Failures
- Higher MTBF indicates more reliable equipment
- Used for maintenance planning, reliability comparison, and improvement tracking
- Availability = MTBF / (MTBF + MTTR)

## Common Misconceptions

**MTBF predicts when the next failure will occur.** MTBF is an average, not a prediction for individual units. A machine with 500-hour MTBF might fail at 100 hours or run 1,000 hours. Failure timing is probabilistic, not deterministic.

**MTBF applies to individual components and whole systems the same way.** System MTBF depends on component arrangement (series vs. parallel) and individual component MTBFs. A system with many series components has lower MTBF than its individual parts.

## Related Tool

Factor equipment reliability into your line balance by stacking each operator's work content against takt time with the free [Yamazumi chart builder](/tools/yamazumi).

Source: https://kaizumi.com/dictionary/mtbf
Licence: free to quote and cite with attribution to Kaizumi.