---
title: "Mean Time Between Failures (MTBF) — monitoring glossary"
description: "Mean Time Between Failures (MTBF) is the average time a system operates between one incident and the next. MTBF measures how reliable something is; MTTR…"
canonical: "https://lemwatch.com/glossary/mtbf"
source: "https://lemwatch.com"
---

# Mean Time Between Failures (MTBF)

> Mean Time Between Failures (MTBF) is the average time a system operates between one incident and the next. MTBF measures how reliable something is; MTTR measures how quickly you recover. Together they define uptime: uptime = MTBF / (MTBF + MTTR).

## Definition

 MTBF is calculated over a fixed window (usually 30-90 days) by dividing total uptime by the number of incidents. A service with 720 hours of uptime and 4 incidents has an MTBF of 180 hours.

 MTBF is the reliability lever engineering owns most directly: better testing, staged rollouts, redundant infrastructure, capacity planning. MTTR is the response lever ops owns: paging, runbooks, automated remediation.

## Why it matters

 Uptime targets are hit by pushing MTBF up or MTTR down. If your MTTR is already tight, pushing MTBF is the only lever left — that means fewer risky deploys, better tests, and change-freeze windows around peak traffic.


## Related

- [Monitoring glossary](https://lemwatch.com/glossary)
- [MTTR](https://lemwatch.com/glossary/mttr)
- [Uptime](https://lemwatch.com/glossary/uptime)
- [SLA](https://lemwatch.com/glossary/sla)
- [Incident](https://lemwatch.com/glossary/incident)
- [Service Level Objective](https://lemwatch.com/glossary/slo)
- [All monitoring checks](https://lemwatch.com/features)
- [Website Monitoring](https://lemwatch.com/glossary/monitoring)