Calculate Mean Time Between Failures and Mean Time To Repair. Measure system reliability and availability metrics.
MTBF (Mean Time Between Failures) and MTTR (Mean Time to Repair/Recover) are reliability engineering metrics that quantify system dependability. MTBF measures how long a system operates before failing, while MTTR measures how quickly it can be restored after a failure. Together, they determine system availability — the percentage of time a system is operational.
These metrics are critical for IT infrastructure planning, SLA definition, disaster recovery design, and capacity planning. Understanding your actual MTBF and MTTR enables data-driven decisions about redundancy investments, maintenance schedules, and recovery strategies.
| Metric | Full Name | Formula | Measures |
|---|---|---|---|
| MTBF | Mean Time Between Failures | Total uptime / Number of failures | How long before the next failure |
| MTTR | Mean Time to Repair | Total repair time / Number of repairs | How long to fix a failure |
| MTTF | Mean Time to Failure | Total operation time / Number of failures | For non-repairable systems |
| MTTA | Mean Time to Acknowledge | Total acknowledge time / Number of incidents | Response team alertness |
| MTTD | Mean Time to Detect | Total detection time / Number of incidents | Monitoring effectiveness |
| Availability | System uptime percentage | MTBF / (MTBF + MTTR) | Overall system reliability |
| Scenario | MTBF | MTTR | Availability | Annual Downtime |
|---|---|---|---|---|
| Legacy server | 2,000 hours | 8 hours | 99.60% | 35 hours |
| Modern cloud | 8,000 hours | 1 hour | 99.99% | 52 minutes |
| With redundancy | 50,000 hours | 0.5 hours | 99.999% | 5 minutes |
MTBF (Mean Time Between Failures) measures the average time a system operates before experiencing a failure, indicating reliability. MTTR (Mean Time To Repair) measures the average time required to restore a system after a failure occurs. Together, these metrics help organizations understand both how often systems fail and how quickly they can be recovered.
System availability is calculated using the formula: Availability = MTBF / (MTBF + MTTR). This gives you the percentage of time a system is expected to be operational. For example, if MTBF is 1000 hours and MTTR is 2 hours, availability would be 99.8%. Higher MTBF or lower MTTR both improve overall availability.
In a series configuration, all components must work for the system to function, so overall reliability decreases as you add components. In a parallel configuration, the system works as long as at least one component is operational, so adding redundant components increases reliability. This calculator helps you model both configurations to design more resilient systems.
The downtime cost calculator multiplies your expected annual downtime hours by your hourly cost of downtime. It accounts for revenue loss, productivity impact, and reputation damage. The tool also shows potential savings from reliability improvements, helping you justify investments in better infrastructure or redundancy.
The SLA compliance mode calculates what availability percentage you need to meet common SLA targets like 99.9% (three nines), 99.99% (four nines), or 99.999% (five nines). It shows allowed monthly downtime for each level and helps you determine if your current MTBF and MTTR metrics can achieve your SLA commitments.
The incident analyzer mode lets you input failure timestamps and repair durations from historical data. It automatically calculates MTBF, MTTR, and failure rates based on your actual incidents. This is more accurate than theoretical calculations because it reflects your real-world operational experience.
Failure rate is the inverse of MTBF and represents how many failures you can expect per unit of time. If your MTBF is 1000 hours, your failure rate is 0.001 failures per hour. This metric is useful for planning maintenance schedules and spare parts inventory, as it tells you approximately when to expect the next failure.