Machine Availability Calculator
Measure availability from a shift's records, or from MTBF and MTTR.
What this calculator does
The user selects the method explicitly. The two methods are never combined, and the method used is shown with the result.
Inputs and what they mean
- How do you want to measure availability?
- — Two published ways of measuring the same idea. They use different inputs and are never mixed in one result..
- Planned production time
- — Used by the period method..
- Unplanned downtime inside that time
- — Used by the period method..
- Mean time between failures (MTBF)
- — Used by the reliability method..
- Mean time to repair (MTTR)
- — Used by the reliability method..
How to use it
- Enter your own figures — the calculator never fills in a rate, price or benchmark for you.
- Press Calculate to see the result.
- Read the formula, variables, assumptions and source below the result before you rely on it.
Formula
Period method: Availability = (Planned production time − Downtime) ÷ Planned production time × 100; Reliability method: Availability = MTBF ÷ (MTBF + MTTR) × 100
Worked example
Availability from a shift's own records
The reliability method is there when you have MTBF and MTTR instead; you choose which one you are using.
Reading the result
The headline figure is the main answer. Any breakdown underneath shows the parts that make it up, so you can check the working and see what changes when you adjust an input.
Limitations and assumptions
Results depend entirely on the figures you enter and are rounded for display. They are for general information and education, not professional advice.
Reference: National Institute of Standards and Technology, Manufacturing Extension Partnership — Lean manufacturing measures: takt time and overall equipment effectiveness
Last reviewed:
Common questions
Formula, source and verification
Two published ways of measuring availability. The user selects which one they are using and only that one's inputs are used.
The question it answers: How much of the period was this machine actually available, and how much of it did we use?
The formula
Period method: Availability = (Planned production time − Downtime) ÷ Planned production time × 100; Reliability method: Availability = MTBF ÷ (MTBF + MTTR) × 100
- PPT — Planned production time
- (h). Period method. Scheduled time excluding planned shutdowns.
- D — Downtime
- (h). Period method. Unplanned stops inside the planned time.
- MTBF — Mean time between failures
- (h). Reliability method. Mean operating time between failures.
- MTTR — Mean time to repair
- (h). Reliability method. Mean time to restore the machine.
Units: Hours in; percentage out.
What kind of calculation this is
Deterministic formula. The same inputs always give the same answer. The maths is fixed and does not depend on judgement.
Method
The user selects the method explicitly. The two methods are never combined, and the method used is shown with the result.
Assumptions built into the result
- Mathematical: Every quantity, time and rate is the figure the user entered, measured over the period they describe.
- Mathematical: Times and counts refer to the same period and the same resource.
- Mathematical: Planned production time already excludes planned shutdowns, on the plant's own definition.
Figures this calculator will never guess for you
- No industry benchmark, target utilisation or target availability is supplied or applied.
- No shift length, break allowance, downtime allowance or standard rate is assumed.
- Optional components are excluded from the result when left at zero.
- The two methods are never averaged or combined, and no availability target is applied to the result.
Limitations
- Arithmetic over the figures entered — it cannot tell whether the measurements behind them are right.
- A measured result, an industry benchmark and an organisation's target are three different things; only the entered figures are used.
- Availability is one factor of overall equipment effectiveness; on its own it says nothing about speed or quality.
Source and version
- Standard or reference
- Equipment availability — the availability factor of overall equipment effectiveness — NIST MEP (Availability as defined in the lean manufacturing guidance published by NIST MEP — run time as a share of planned production time; the reliability form expresses the same idea as mean time between failures over mean time between failures plus mean time to repair.)
- Published source
- National Institute of Standards and Technology, Manufacturing Extension Partnership — MEP guidance
- Formula version
- Version 1
- Verification
- Reviewed against the cited source on
- How much weight the source carries
- Standards or government
- Applies to
- Currency
- The result is a ratio or index, so it does not depend on currency.
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