In microeconomics, economies of scale are the cost advantages that enterprises obtain due to their scale of operation, and are typically measured by the amount of output produced per unit of cost (production cost). A decrease in cost per unit of output enables an increase in scale that is, increased production with lowered cost. The basis of economies of scale may be technical, statistical, organizational or related factors to the degree of market control.

Economies of scale arise in various organizational and business situations and at various levels, such as a production, plant or an entire enterprise. When average costs decline as output increases, then economies of scale occur. Some economies of scale, such as capital cost of manufacturing facilities and friction loss of transportation and industrial equipment, have a physical or engineering basis. The economic concept dates back to Adam Smith and the idea of obtaining larger production returns through the use of division of labor. Diseconomies of scale are the opposite.

Economies of scale often have limits, such as passing the optimum design point where costs per additional unit begin to increase. Common limits include exceeding the nearby raw material supply, such as wood in the lumber, pulp and paper industry. A common limit for a low cost per unit weight raw materials is saturating the regional market, thus having to ship products uneconomic distances. Other limits include using energy less efficiently or having a higher defect rate.

Large producers are usually efficient at long runs of a product grade (a commodity) and find it costly to switch grades frequently. They will, therefore, avoid specialty grades even though they have higher margins. Often smaller (usually older) manufacturing facilities remain viable by changing from commodity-grade production to specialty products. Landes describes the problem of new steel mills in late 19th century Britain being too large for the market and unable to economically produce short production runs of specialty grades. The old mills had another advantage in that they were fully amortized. Economies of scale must be distinguished from economies stemming from an increase in the production of a given plant. When a plant is used below its optimal production capacity, increases in its degree of utilization bring about decreases in the total average cost of production. Nicholas Georgescu-Roegen (1966) and Nicholas Kaldor (1972) both argue that these economies should not be treated as economies of scale.

Overview The simple meaning of economies of scale is doing things more efficiently with increasing size. Chandler uses the example of high turn over in distribution. Common sources of economies of scale are purchasing (bulk buying of materials through long-term contracts), managerial (increasing the specialization of managers), financial (obtaining lower-interest charges when borrowing from banks and having access to a greater range of financial instruments), marketing (spreading the cost of advertising over a greater range of output in media markets), and technological (taking advantage of returns to scale in the production function). Each of these factors reduces the long run average costs (LRAC) of production by shifting the short-run average total cost (SRATC) curve down and to the right.

Economies of scale is a concept that may explain patterns in international trade or in the number of firms in a given market. The exploitation of economies of scale helps explain why companies grow large in some industries. It is also a justification for free trade policies, since some economies of scale may require a larger market than is possible within a particular country—for example, it would not be efficient for Liechtenstein to have its own carmaker if they only sold to their local market. A lone carmaker may be profitable, but even more so if they exported cars to global markets in addition to selling to the local market. Economies of scale also play a role in a "natural monopoly". There is a distinction between two types of economies of scale: internal and external. An industry that exhibits an internal economy of scale is one where the costs of production fall when the number of firms in the industry drops, but the remaining firms increase their production to match previous levels. Conversely, an industry exhibits an external economy of scale when costs drop due to the introduction of more firms, thus allowing for more efficient use of specialized services and machinery.

Economies of scale exist whenever the total cost of producing two quantities of a product X is lower when a single firm instead of two separate firms produce it. See Economies of scope#Economics.

Determinants of economies of scale Physical and engineering basis: economies of increased dimension Some of the economies of scale recognized in engineering have a physical basis, such as the square–cube law, by which the surface of a vessel increases by the square of the dimensions while the volume increases by the cube. This law has a direct effect on the capital cost of such things as buildings, factories, pipelines, ships and airplanes.

In structural engineering, the strength of beams increases with the cube of the thickness.

Drag loss of vehicles like aircraft or ships generally increases less than proportional with increasing cargo volume, although the physical details can be quite complicated. Therefore, making them larger usually results in less fuel consumption per ton of cargo at a given speed.

Heat loss from industrial processes vary per unit of volume for pipes, tanks and other vessels in a relationship somewhat similar to the square–cube law. In some productions, an increase in the size of the plant reduces the average variable cost, thanks to the energy savings resulting from the lower dispersion of heat.

Economies of increased dimension are often misinterpreted because of the confusion between indivisibility and three-dimensionality of space. This confusion arises from the fact that three-dimensional production elements, such as pipes and ovens, once installed and operating, are always technically indivisible. However, the economies of scale due to the increase in size do not depend on indivisibility but exclusively on the three-dimensionality of space. Indeed, indivisibility only entails the existence of economies of scale produced by the balancing of productive capacities, considered above; or of increasing returns in the utilisation of a single plant, due to its more efficient use as the quantity produced increases. However, this latter phenomenon has nothing to do with the economies of scale which, by definition, are linked to the use of a larger plant.

Economies in holding stocks and reserves At the base of economies of scale there are also returns to scale linked to statistical factors. In fact, the greater of the number of resources involved, the smaller, in proportion, is the quantity of reserves necessary to cope with unforeseen contingencies (for instance, machine spare parts, inventories, circulating capital, etc.).

Transaction economies One of the reasons firms appear is to reduce transaction costs. A larger scale generally determines greater bargaining power over input prices and therefore benefits from pecuniary economies in terms of purchasing raw materials and intermediate goods compared to companies that make orders for smaller amounts. In this case, we speak of pecuniary economies, to highlight the fact that nothing changes from the "physical" point of view of the returns to scale. Furthermore, supply contracts entail fixed costs which lead to decreasing average costs if the scale of production increases. This is of important utility in the study of corporate finance.

Economies deriving from the balancing of production capacity Economies of productive capacity balancing derives from the possibility that a larger scale of production involves a more efficient use of the production capacities of the individual phases of the production process. If the inputs are indivisible and complementary, a small scale may be subject to idle times or to the underutilization of the productive capacity of some sub-processes. A higher production scale can make the different production capacities compatible. The reduction in machinery idle times is crucial in the case of a high cost of machinery.

Economies resulting from the division of labour and the use of superior techniques A larger scale allows for a more efficient division of labour. The economies of division of labour derive from the increase in production speed, from the possibility of using specialized personnel and adopting more efficient techniques. An increase in the division of labour inevitably leads to changes in the quality of inputs and outputs.; On the relationship between built-in technical change and scale growth, see .

Managerial economics Many administrative and organizational activities are mostly cognitive and, therefore, largely independent of the scale of production. shows how these economies of scale in the acquisition of specialized knowledge play an essential role in the existence of the company. When the size of the company and the division of labour increase, there are a number of advantages due to the possibility of making organizational management more effective and perfecting accounting and control techniques. Furthermore, the procedures and routines that turned out to be the best can be reproduced by managers at different times and places.

Learning and growth economies Learning and growth economies are at the base of dynamic economies of scale, associated with the process of growth of the scale dimension and not to the dimension of scale per se. Learning by doing implies improvements in the ability to perform and promotes the introduction of incremental innovations with a progressive lowering of average costs. Learning economies are directly proportional to the cumulative production (experience curve). Growth economies emerge if a company gains an added benefit by expanding its size. These economies are due to the presence of some resource or competence that is not fully utilized, or to the existence of specific market positions that create a differential advantage in expanding the size of the firms. That growth economies disappear once the scale size expansion process is completed. For example, a company that owns a supermarket chain benefits from an economy of growth if, opening a new supermarket, it gets an increase in the price of the land it owns around the new supermarket. The sale of these lands to economic operators, who wish to open shops near the supermarket, allows the company in question to make a profit, making a profit on the revaluation of the value of building land.

Capital and operating cost Overall costs of capital projects are known to be subject to economies of scale. A crude estimate is that if the capital cost for a given sized piece of equipment is known, changing the size will change the capital cost by the 0.6 power of the capacity ratio (the point six to the power rule).

In estimating capital cost, it typically requires an insignificant amount of labor, and possibly not much more in materials, to install a larger capacity electrical wire or pipe having significantly greater capacity.See various estimating guides that publish tables of tasks commonly encountered in building trades with estimates of labor hours and costs per hour for the trade, often with regional pricing.

The cost of a unit of capacity of many types of equipment, such as electric motors, centrifugal pumps, diesel and gasoline engines, decreases as size increases. Also, the efficiency increases with size.See various engineering handbooks and manufacturers' data.

Crew size and other operating costs for ships, trains and airplanes