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Table 11.1 Input and output capacity measures for different operations
Chapter 11 Capacity planning and control 305
Operation Input measure of capacity Output measure of capacity
Air-conditioner plant Machine hours available Number of units per week
Hospital Beds available Number of patients treated per week
Theatre Number of seats Number of customers entertained per week
University Number of students Students graduated per year
Retail store Sales floor area Number of items sold per day
Airline Number of seats available Number of passengers per week
on the sector
Electricity company Generator size Megawatts of electricity generated
Brewery Volume of fermentation tanks Litres per week
Note: The most commonly used measure is shown in bold.
its patients required relatively minor treatment with only short stays in hospital, it could
treat many people per week. Alternatively, if most of its patients required long periods of
observation or recuperation, it could treat far fewer. Output depends on the mix of activities
in which the hospital is engaged and, because most hospitals perform many different types of
activities, output is difficult to predict. Certainly it is difficult to compare directly the capacity
of hospitals which have very different activities.
Worked example
Suppose an air-conditioner factory produces three different models of air-conditioner
unit: the de luxe, the standard and the economy. The de luxe model can be assembled in
1.5 hours, the standard in 1 hour and the economy in 0.75 hour. The assembly area
in the factory has 800 staff hours of assembly time available each week.
If demand for de luxe, standard and economy units is in the ratio 2:3:2, the time
needed to assemble 2 + 3 + 2 = 7 units is:
The number of units produced per week is:
(2 × 1.5) + (3 × 1) + (2 × 0.75) = 7.5 hours
800
7.5
× 7 = 746.7 units
If demand changes to a ratio of de luxe, economy, standard units of 1:2:4, the time
needed to assemble 1 + 2 + 4 = 7 units is:
(1 × 1.5) + (2 × 1) + (4 × 0.75) = 6.5 hours
Now the number of units produced per week is:
800
6.5
× 7 = 861.5 units
Design capacity
Design capacity and effective capacity
The theoretical capacity of an operation – the capacity which its technical designers had
in mind when they commissioned the operation – cannot always be achieved in practice.
For example, a company coating photographic paper will have several coating lines which
deposit thin layers of chemicals onto rolls of paper at high speed. Each line will be capable of
running at a particular speed. Multiplying the maximum coating speed by the operating time
of the plant gives the theoretical design capacity of the line. But in reality the line cannot be