Free to use No signup Event log based

MTBF & MTTR Reliability Calculator

Measure system reliability and maintainability from your uptime and downtime event log. Visual timeline and availability metrics included.

Averages only. MTBF assumes a constant failure rate (the "useful life" phase of the bathtub curve). It does not predict infant mortality or wear-out failures. Use Weibull analysis for lifecycle predictions.

Use the calculator
Dual metricsMTBF + MTTR + Availability
Event logAdd/remove uptime & downtime
Visual timelineGantt-style event chart
Export reportTXT download & WhatsApp

MTBF & MTTR Calculator

Log your system's uptime and downtime events in hours.

No events logged yet. Add uptime and downtime periods above.

What this calculator covers

Reliability engineering metrics from your operational event log.

MTBF & MTTR

Mean Time Between Failures and Mean Time To Repair.

Event log

Add, remove, and validate uptime/downtime periods.

Visual timeline

Gantt-style chart of all logged events.

Export report

TXT summary or WhatsApp share of your metrics.

Built and maintained by Bhavin Sheth
Last modified: Oct 12, 2026
Reliability engineering

Formulas & worked examples

The standard maintenance metrics and how to interpret them.

01

MTBF — Reliability

Mean Time Between Failures.

Use case

A plant manager comparing two production lines to decide which needs a reliability upgrade or preventive maintenance schedule.

Formula & example

MTBF = Total Uptime ÷ Number of Failures
1000 hrs uptime, 2 failures → 500 hrs MTBF
Higher is better — indicates fewer failures.

Who uses it

  • Maintenance engineers
  • Reliability analysts
  • Asset managers
02

MTTR — Maintainability

Mean Time To Repair.

Use case

An IT team measuring how quickly their incident response team restores services after an outage, tracking SLA compliance.

Formula & example

MTTR = Total Downtime ÷ Number of Failures
4 hrs downtime, 2 failures → 2 hrs MTTR
Lower is better — indicates faster repairs.

Who uses it

  • IT operations
  • Service desk managers
  • Field service teams
03

Availability

Percentage of uptime.

Use case

A data center reporting "five nines" (99.999%) availability to customers as part of their service level agreement.

Formula & example

Availability = MTBF ÷ (MTBF + MTTR)
500 hrs MTBF, 2 hrs MTTR → 99.60% availability
Closer to 100% is better.

Who uses it

  • SaaS providers
  • Telecom operators
  • Utility companies
Honest by design

What this calculator includes — and what it leaves out

Standard reliability metrics; the statistical limits are named, not hidden.

Tool limits

  • Assumes constant failure rate (exponential distribution)
  • Does not model the bathtub curve phases
  • Requires at least one downtime event to calculate metrics
  • Works on desktop, tablet, and mobile with no install

What this tool does

  • Calculates MTBF, MTTR, and Availability from event logs
  • Validates for overlapping events and negative times
  • Draws a Gantt-style timeline and pie chart
  • Exports a TXT report or shares via WhatsApp

What this tool does NOT do

  • It doesn't perform Weibull analysis or predict future failures
  • It doesn't account for censored data (systems still running)
  • Calculations run in your browser; the tool does not save your inputs
  • It isn't a substitute for a full reliability engineering study

Standards & references

Where these reliability metrics come from, plus related tools on this site.

Questions about reliability metrics

Straight answers on MTBF, MTTR, availability, and their limitations.

MTBF & reliability

What is the difference between MTTR and MTBF?

MTBF (Mean Time Between Failures) measures the average time a system runs before it fails, indicating reliability. A high MTBF is good. MTTR (Mean Time to Repair) measures the average time it takes to fix a failure, indicating maintainability. A low MTTR is good.

How are MTTR and MTBF calculated?

MTBF equals Total Uptime divided by Number of Failures. MTTR equals Total Downtime divided by Number of Failures. Our calculator automates this process based on the event log you provide.

Why is a high MTBF important?

A high MTBF means your system or equipment is very reliable and fails infrequently. This leads to higher productivity, lower unexpected maintenance costs, and better customer satisfaction if it's a customer-facing service.

MTTR & availability

Why is a low MTTR important?

A low MTTR indicates that your team can diagnose and resolve issues quickly. This minimizes the impact of failures, reduces overall downtime, and gets your systems back to productive work faster.

What is system availability?

Availability is the percentage of time a system is operational. It is calculated as MTBF / (MTBF + MTTR) or Total Uptime / (Total Uptime + Total Downtime).

Can I use this calculator for any type of system?

Yes. As long as you can define periods of uptime and downtime, you can use this tool. It's applicable to manufacturing machinery, IT servers, software services, vehicle fleets, and more.

Measure your system's reliability today

No signup required. MTBF, MTTR, and availability from your event log — computed in your browser.

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