Machine Availability Formula and Calculator
Availability = run time ÷ planned production time. Enter one shift or one week for a machine or line and see its availability, what planned stops do to the number, and inherent availability from breakdowns alone. Numbers update as you type.
Updated October 2026
Your machine or line
Use one period for every number: a shift, a day or a week, in minutes.
Where the scheduled time went
Several machines? Compare them here
Combined availability is total run time ÷ total planned production time. A plain average of the percentages is shown next to it so you can see the difference.
| Machine | Planned time (min) | Stop time (min) | Availability |
|---|---|---|---|
| Machine A | - | ||
| Machine B | - | ||
| Machine C | - | ||
| Combined, by time | - | ||
Track availability every shift, free.
The free OEE Tracker logs each shift and instantly shows your OEE, your downtime Pareto and how you compare to your industry, then keeps your history and builds your trend for you.
Open the free OEE TrackerMost lost availability is preventable, once you can see the cause.
Downtime you can't diagnose, you can't stop. Fabrico tracks downtime live from PLCs, IoT sensors or AI cameras. Where cameras are fitted, the video of a stop sits next to its machine data with AI-suggested likely causes the team validates, and a technician opens the work order from the stop, so the same failure stops repeating.
Book a Fabrico demo See how Fabrico tracks machine downtimeThe availability formula
Availability = Run Time ÷ Planned Production Time
- Planned production time = scheduled time minus planned stops (breaks and time with no intention to run).
- Run time = planned production time minus stop time (breakdowns, other unplanned stops, changeovers and setups).
This follows the OEE definition from Nakajima as used in research: availability is planned production time minus downtime, and downtime includes breakdowns and changeovers (source: Hedman, Chalmers PhD thesis, 2016, section 2, read 3 October 2026). Breaks that are planned with no production are left out of planned production time.
A worked example
The numbers the calculator opens with: an 8 hour shift with an hour of breaks, 30 minutes of breakdowns, 15 minutes of waiting and a 25 minute changeover.
| Step | Calculation | Result |
|---|---|---|
| Planned production time | 480 - 60 | 420 min |
| Stop time | 30 + 15 + 25 | 70 min |
| Run time | 420 - 70 | 350 min |
| Availability | 350 ÷ 420 | 83.3% |
Planned stops: in or out?
This is the question most availability numbers get wrong. If the breaks are left in planned production time and counted as downtime, the same shift reads 350 ÷ 480 = 72.9% instead of 83.3%. Neither number is false, but they cannot be compared with each other. The common OEE practice is to take planned stops out of planned production time, and to count everything that happens while the machine is meant to run, changeovers included, as stop time. Decide which stops are planned, write it down, and keep it for every machine and every period.
Operational vs inherent availability
The availability above is operational availability: every stop counts. Maintenance teams also use inherent availability, which looks only at failures and repairs:
Inherent availability = MTBF ÷ (MTBF + MTTR)
In the example, 2 breakdowns in 350 minutes of run time give an MTBF of 175 minutes and an MTTR of 15 minutes, so inherent availability is 175 ÷ 190 = 92.1%. The gap between 92.1% and 83.3% is the time lost to everything that is not a failure: waiting and changeovers. Work out MTBF and MTTR in more detail with the MTBF and MTTR calculator and the guide on how to calculate MTTR.
Availability for several machines
Combine machines by time, not by percentage. With the three machines in the comparison table, total run time is 350 + 390 + 180 = 920 minutes out of 1,080 planned, so combined availability is 85.2%. The plain average of the three percentages is 83.7%, because it gives the short-running machine C as much weight as the others.
How availability fits into OEE
Availability is the first of the three OEE factors: OEE = availability × performance × quality. A high availability with low OEE points at speed losses or rejects instead; work them out with the OEE calculator or read what OEE is.
Common mistakes
- Counting breaks or no-demand time as downtime on some machines and not on others.
- Leaving changeovers out of stop time because they were planned.
- Missing the short stops nobody logs; they belong in stop time or in performance, but somewhere.
- Averaging availability percentages across machines or shifts instead of adding up the minutes.
- Comparing inherent availability on one line with operational availability on another.
Availability FAQ
What is the formula for machine availability?
Divide run time by planned production time. Planned production time is the scheduled time minus planned stops such as breaks; run time is planned production time minus every stop, including breakdowns, waiting and changeovers.
Should planned stops count against availability?
Usually no. The common OEE practice is to take planned stops, such as breaks and time with no demand, out of planned production time before you calculate availability. Write down which stops you treat as planned and keep it the same, or the trend means nothing.
Do changeovers count against availability?
Yes. Changeovers and setups happen inside planned production time, so they are availability losses in OEE, even when they are planned.
Is idle time downtime?
If the machine was scheduled and could have run but waited for material, an operator or a decision, count it as a stop. If there was no demand and no intention to run, take it out of planned production time like a planned stop.
What is the difference between inherent and operational availability?
Inherent availability looks only at failures and repairs: MTBF ÷ (MTBF + MTTR). Operational availability, the one OEE uses, counts every stop in planned production time, so it is always the lower of the two.
How do I combine availability for several machines?
Add up the run time of all machines and divide by their total planned production time. Averaging the percentages gives the wrong answer when the machines ran for different amounts of time.
Related: how to calculate availability · OEE calculator · MTBF / MTTR calculator · the six big losses