--- title: "MTBF: what it is and how to calculate it | attendo" description: "What MTBF (mean time between failures) is, how to calculate it with an example, what it is for and the usual mistake: calculating it on an incomplete history." url: "https://attendo.me/en/glossary/mtbf" lang: "en" --- # MTBF: what it is and how to calculate it Also known as: Mean time between failures MTBF (mean time between failures) is the average time a piece of equipment runs properly between one breakdown and the next. It measures reliability. How to calculate it MTBF = total operating time ÷ number of failures in that period ## How to calculate it Divide the time the equipment has been in service by the number of failures in that period. A machine that has run for 1,800 hours and failed 3 times has an MTBF of 600 hours. The higher it is, the more reliable the equipment. ## What it is not It is not the service life, nor a promise that the equipment will last that long. It is an average: it helps you **compare** equipment and **spot trends**, not predict when a specific machine will fail. ## What it is for - Comparing two machines of the same family and spotting the one that is deteriorating. - Justifying a replacement with data rather than gut feeling. - Sizing spare parts stock to the real failure rate. - Knowing whether the [preventive](https://attendo.me/en/glossary/preventive-maintenance) plan works: if MTBF goes up, it works. ## The usual mistake Calculating it on an incomplete history. If half the breakdowns were fixed without logging a work order, MTBF comes out twice as good as it really is. The metric is only as good as the records behind it. ## In attendo [attendo CMMS](https://attendo.me/en/cmms) calculates MTBF by asset and by family from closed work orders, next to MTTR and the ratio of corrective to preventive work. - [attendo CMMS](https://attendo.me/en/cmms) ## Where it is used in attendo ### Modules - [Assets and inventory](https://attendo.me/en/modules/assets): Each asset with its own record, QR code, history and readings - [AI-CMMS](https://attendo.me/en/modules/ai-cmms): The AI in attendo CMMS: probable diagnosis and criticality - [Reports and dashboards](https://attendo.me/en/modules/reports-and-dashboards): Reports and dashboards for every area, with today’s data ### Industries that use these modules - [IT services and MSPs](https://attendo.me/en/industries/it-services) - [Manufacturing and industrial plants](https://attendo.me/en/industries/manufacturing) - [Energy and renewables](https://attendo.me/en/industries/energy-renewables) - [Hospitality, retail and multi-site](https://attendo.me/en/industries/multi-site-operations) - [And any other business](https://attendo.me/en/industries) ## Related terms Maintenance ### MTTR Mean time to repair MTTR (mean time to repair) is the average time it takes to bring equipment back into service after it fails. It measures responsiveness, not reliability. Maintenance ### Availability Asset availability Availability is the percentage of time an asset is in a condition to operate. Maintenance ### Preventive maintenance PM Preventive maintenance is work planned by calendar or by usage to keep failures from happening: routine inspections, lubrication, scheduled replacements and regulatory checks. ### On the blog #### How to calculate MTBF and MTTR without fooling yourself Both formulas fit on one line. The hard part is making the number mean something. Here are the formulas, a complete example and the three mistakes that turn these KPIs into decoration. 4 min read #### The five maintenance KPIs that actually matter There are lists of thirty maintenance KPIs out there, and almost nobody uses thirty. These are five that change decisions, each with its trap, plus the ones you can usually drop. 4 min read [See all 53 glossary terms](https://attendo.me/en/glossary) ## Shall we look at it with your data? We will show you how what you just read works in attendo, with your own assets, tickets and customers. If it is not a fit, we will tell you. - With your operation, not a generic demo - A real person from our team replies - No cold calls afterwards Would you rather talk first? - Phone [+34 910 053 530](tel:+34910053530) - Email [sales@attendo.me](mailto:sales@attendo.me) - Monday to Thursday 9:30 AM to 6:30 PM and Friday 9:30 AM to 2:30 PM (Spain time)