How to Calculate MTBF and MTTR for Your Equipment

If you manage maintenance for any operation, two metrics matter more than almost anything else: MTBF and MTTR. They tell you how reliable your equipment is and how efficiently your team responds to failures.

What is MTBF?

MTBF (Mean Time Between Failures) measures the average time between equipment breakdowns. A higher MTBF means more reliable equipment.

How to Calculate MTBF

MTBF = Total Operating Time / Number of Failures

Example: A pump runs for 2,000 hours over 6 months and fails 4 times.

MTBF = 2,000 hours / 4 failures = 500 hours

This means the pump averages 500 hours of operation between breakdowns.

What MTBF Tells You

• High MTBF — Equipment is reliable; your PM program is working
• Low MTBF — Equipment fails frequently; investigate root causes
• Declining MTBF — Equipment is degrading; consider replacement or increased maintenance
• Improving MTBF — Your maintenance improvements are paying off

What is MTTR?

MTTR (Mean Time To Repair) measures the average time it takes to restore equipment to operation after a failure. A lower MTTR means faster repairs.

How to Calculate MTTR

MTTR = Total Repair Time / Number of Repairs

Example: That same pump had 4 failures. The repair times were 2 hours, 4 hours, 1.5 hours, and 2.5 hours.

Total Repair Time = 2 + 4 + 1.5 + 2.5 = 10 hours
MTTR = 10 hours / 4 repairs = 2.5 hours

The average repair takes 2.5 hours.

What MTTR Tells You

• High MTTR — Repairs take too long; investigate bottlenecks
• Low MTTR — Your team responds and resolves quickly
• Increasing MTTR — Parts availability, skill gaps, or equipment complexity may be issues
• Decreasing MTTR — Procedures, training, or parts stocking improvements are working

Common MTTR Bottlenecks

When MTTR is too high, these are the usual culprits:

1. Diagnosis time — Technicians spend hours figuring out what’s wrong
2. Parts availability — Waiting for spare parts that aren’t in stock
3. Skill mismatch — Wrong technician assigned to the repair
4. Documentation gaps — No procedures or manuals available at the point of repair
5. Approval delays — Waiting for authorization to proceed with repairs

Using MTBF and MTTR Together

The real power comes from combining these metrics:

Equipment Availability

Availability = MTBF / (MTBF + MTTR) × 100%

Using our pump example:

Availability = 500 / (500 + 2.5) × 100% = 99.5%

Comparing Assets

When you track MTBF and MTTR across your asset fleet, patterns emerge:

• Low MTBF + High MTTR — Your worst performers; prioritize these for PM or replacement
• High MTBF + Low MTTR — Your best performers; study what’s working
• Low MTBF + Low MTTR — Frequent but quick fixes; may indicate a recurring root cause
• High MTBF + High MTTR — Rare but difficult failures; ensure parts and procedures are ready

How to Track MTBF and MTTR

Manual tracking with spreadsheets works but is error-prone and time-consuming. You need to record:

• Every failure event with timestamp
• Every repair completion with timestamp
• Operating hours between failures

A CMMS automates this. When technicians close work orders, the system calculates MTBF and MTTR automatically. Reports show trends over time and flag assets that need attention.

Setting Targets

There’s no universal “good” MTBF or MTTR — targets depend on your equipment, industry, and criticality levels. Start by baselining your current numbers, then set improvement targets:

• First 90 days — Establish baselines for your critical assets
• 6 months — Aim for 10-15% improvement in MTBF through PM
• 12 months — Aim for 20-30% reduction in MTTR through better procedures and parts stocking

Key Takeaways

• MTBF measures reliability (higher is better)
• MTTR measures repair efficiency (lower is better)
• Together they calculate equipment availability
• Track both metrics over time to measure improvement
• Use a CMMS to automate calculation and reporting
• Start with your most critical assets and expand from there