 Isoquant is also called as equal product curve or production indifference curve or constant product curve. Isoquant indicates various combinations of two factors of production which give the same level of output per unit of time.  Just as an indifference curve represents various combinations of two goods which give a consumer equal amount of satisfaction, an iso-product curve shows all possible combinations of two inputs physically capable of producing a given level of output. Since an iso-product curve represents those combinations which will result in the production of an equal quantity of output, the producer would be indifferent between them.  This law was given by Alfred Marshall in his book principle of economics.  It show particular pattern of change in output when some factor remain fixed.  Production depend upon factors of production , if factors of production are good, production may increase and vice-versa.  Production function show functional relationship between production and factors of production.  It refers to manner of change in output cost by the increase in all the input simultaneously and in the same proportion.  Returns refers to “change in physical output”  Scale refers to “quantity of input employed”  Change in scale means that all factors of production are increased or decreased in same proportion.  The cost advantage that arises with increased output of a product.  It arises because of the inverse relationship between the quantity produced and per-unit fixed cost.  Profit refers to the excess of receipts from the sale of goods over the expenditure incurred on producing them.  The amount received from the sale of goods is known as ‘revenue’ and the expenditure on production of such goods is termed as ‘cost’. The difference between revenue and cost is known as ‘profit’.  For example, if a firm sells goods for Rs. 10 crores after incurring an expenditure of Rs. 7 crores, then profit will be Rs. 3 crores.

1. PRODUCTION – EQUAL PRODUCT CURVES
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2. PRODUCTION – EQUAL PRODUCT CURVES
 Isoquant is also called as equal product curve or production indifference curve or
constant product curve. Isoquant indicates various combinations of two factors of
production which give the same level of output per unit of time.
 Just as an indifference curve represents various combinations of two goods which
give a consumer equal amount of satisfaction, an iso-product curve shows all
possible combinations of two inputs physically capable of producing a given level
of output. Since an iso-product curve represents those combinations which will
result in the production of an equal quantity of output, the producer would be
indifferent between them.
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3. WHAT ARE ISO-PRODUCT CURVES OR EQUAL PRODUCT CURVES?
 It is the business of a manufacturer to hit on the cheapest or the lowest cost
method to produce a given output out of the several alternative methods open to
him. There are a large number of combinations of inputs which can produce a
given output and the producer has to select the most economical combination out
of these. This will be an equilibrium position for him.
 In recent years, a new technique has been developed to study the theory of
production and to show the equilibrium of a producer regarding combination of
factors. This technique is of Iso-product a curve which is a parallel concept to the
indifference curves in the theory of consumption.
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4. FACTOR COMBINATIONS TO PRODUCE A GIVEN OR LEVEL OF
OUTPUT:
The concept of isoquant can be easily understood from above Table. It is presumed
that two factors labor and capital are being employed to produce a product. Each of
the factor combinations A. B, C, D and E produces the same level of output, say 100
units. To start with, factor combination A consisting of 1 unit of labor and 12 units of
capital produces the given 100 units of output. 4

5. Similarly, combination B consisting of 2 units of labor and 8 units of capital,
combination C consisting of 3 units of labor and 5 units of capital, combination D
consisting of 4 units of labor and 3 units of capital, combination E consisting of 5
units of labor and 2 units of capital are capable of producing the same amount of
output, i.e., 100 units. We have plotted all these combinations and by joining them
we obtain an isoquant showing that every combination represented on it can produce
100 units of output.
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6.  Though isoquants are similar to be indifference
curves of the theory of consumer’s behavior,
there is one important difference between the
two. An indifference curve represents all those
combinations of two goods which provide the
same satisfaction or utility to a consumer but no
attempt is made to specify the level of utility in
exact quantitative terms it stands for.
 This is so because the cardinal measurement of
satisfaction or utility in unambiguous thermos is
not possible. That is why we usually label
indifference curves by ordinal numbers as I, II,
III etc. indicating that a higher indifference
curve represents a higher level of satisfaction
than a lower one, but the information as to how
much one level of satisfaction is greater than
another is not provided.
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7.  On the other hand, we can label isoquants in
the physical units of output without any
difficulty. Production of a good being a
physical phenomenon lends itself easily to
absolute measurement in physical units. Since
each isoquant represents a specified level of
production, it is possible to say by how much
one isoquant indicates greater or less
production than another.
 we have drawn an isoquant-map or equal-
product map with a set of four isoquants which
represent 100 units, 120 units, 140 units and
160 units of output respectively. Then, from
this set of isoquants it is very easy to judge by
how much production level on one isoquant
curve is greater or less than on another.
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8. PROPERTIES OF EQUAL PRODUCT CURVES
Properties of iso-product curves are the same as those of indifference curves. Their
properties can also be proved in the same manner as in the case of indifference curves.
The following are the important properties of iso-product curves:
(I)Sloping Downwards- Iso-product curves slope downwards from left to right. This is
so because if the quantity of a factor X is increased, the quantity of factor Y must be
decreased so as to maintain the same level of output.
(ii)Convexity- Iso-product curves are convex to the origin. Thus, it is the diminishing
marginal rate of substitution which is a realistic phenomenon and due to which the iso-
product curves are convex to the origin.
(iii)Non-intersecting-Two iso-product curves cannot cut each other.
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