MTBF vs Availability: How Often It Fails vs How Much It Is Up

Key takeaways

• MTBF (mean time between failures) measures how long an asset runs before failing.
• Availability measures the share of scheduled time the asset is actually up.
• High MTBF does not guarantee high availability if repairs are slow (high MTTR).
• Availability depends on both how often it fails and how fast you recover.

Short answer: MTBF measures reliability — how long an asset typically runs between failures. Availability measures uptime — the share of scheduled time it is actually running. They are linked but distinct: an asset with great MTBF but slow repairs (high MTTR) can still have poor availability. Availability = MTBF ÷ (MTBF + MTTR), so both reliability and repair speed drive it. See also plant availability vs equipment availability.

What MTBF measures

• Average run time between failures.
• A pure reliability metric.
• Improved by eliminating failure causes.

What availability measures

• Share of scheduled time the asset is up.
• Depends on both failure frequency and repair speed.
• Feeds the Availability term of OEE.

How they connect

Availability = MTBF ÷ (MTBF + MTTR). Raise MTBF (fail less) or cut MTTR (repair faster) and availability rises. Focus on only one and the other can hold you back.

Why high MTBF is not enough

An asset that rarely fails but takes a day to fix when it does can still have mediocre availability. Reliability and maintainability both matter — track MTBF and MTTR together.

How OEE relates

Availability is one of OEE’s three terms. MTBF and MTTR are the levers under it: reliability engineering raises MTBF, faster response cuts MTTR, and OEE Availability climbs from both.

See how Fabrico captures this automatically on your lines — explore OEE for manufacturing or book a demo.

Related reading

• plant availability vs equipment availability
• maintenance engineer vs reliability engineer
• oee for manufacturing

Frequently asked questions

Is MTBF the same as availability?

No — MTBF is reliability; availability also depends on repair speed.

What is the formula?

Availability = MTBF ÷ (MTBF + MTTR).

Can high MTBF still mean low availability?

Yes, if repairs are slow.

Which feeds OEE?

Availability — driven by both MTBF and MTTR.