Core Reliability

MTTR Calculator

Mean time to repair from individual repair times or totals — the maintainability half of availability.

MTTR = Σt ÷ n

Calculation Method

Time Unit

Repair Times (hours)

What is MTTR?

Mean Time To Repair (MTTR) is a reliability engineering metric that measures the average time required to repair a failed component or system and restore it to full operational functionality.

MTTR covers the entire repair process from failure detection to restoration, including:

Failure detection and notification
Diagnosis and troubleshooting
Parts procurement and logistics
Actual repair work
Testing and system verification

Definitions differ here: many standards treat MTTR as active repair time only and count waiting for parts and people as logistics delay, part of mean down time (MDT). Say which you are measuring, and use active repair time for inherent availability.

MTTR formula

Basic formula

MTTR = Total repair time ÷ Number of repairs

From individual repairs

MTTR = Σ(individual repair times) ÷ total repairs

Time can be measured in hours, minutes, or days depending on your industry and requirements.

MTTR calculation example

A production line had 5 breakdowns last month with these repair times:

Breakdown	Repair time
1	2.5 h
2	1.8 h
3	4.2 h
4	3.1 h
5	2.4 h

Total repair time

2.5 + 1.8 + 4.2 + 3.1 + 2.4 = 14.0 hours

MTTR

14.0 ÷ 5 = 2.8 hours

MTTR benchmarks

Commonly quoted ranges — useful for orientation; your own trend matters more than any external figure.

Context	Range
Manufacturing — world class	< 1 hour
Manufacturing — good	1 – 4 hours
Manufacturing — average	4 – 8 hours
IT — critical incidents	< 30 minutes
IT — high priority	1 – 4 hours
Automotive production line	15 – 60 minutes
Automotive support equipment	2 – 6 hours

How to use this MTTR calculator

Individual times: enter each repair time separately for detailed analysis
Aggregate data: use total time and repair count for quick calculations
Units: choose hours, minutes, or days to match your data

Best practices:

Include all repair phases in your time measurements
Use consistent time periods for accurate trends
Separate planned and unplanned maintenance
Track MTTR over time to identify improvement trends

Where MTTR is used

Application	Use
Maintenance planning	Schedule resources and plan maintenance windows
SLA management	Set realistic service level agreements
Cost analysis	Calculate downtime costs and maintenance budgets
Performance monitoring	Track maintenance team effectiveness

Frequently asked questions

What’s the difference between MTTR and MTBF?

MTTR measures how long it takes to repair a system after failure, while MTBF measures how long a system operates between failures. MTTR focuses on repair efficiency, MTBF on reliability.

How can I improve my MTTR?

Keep critical spares in stock, train maintenance staff, implement condition monitoring, use better diagnostic tools, and standardise repair procedures.

What should be included in the MTTR calculation?

All time from failure notification to full restoration: detection, diagnosis, parts procurement, repair work, testing, and verification.

Is lower MTTR always better?

Generally yes, but consider the cost-benefit ratio. Extremely low MTTR might require expensive resources. Aim for an MTTR that balances cost and operational requirements.

How often should I calculate MTTR?

Monthly or quarterly for trending. For critical systems, weekly or even daily calculations can help identify issues quickly.