isocost

thumb|500px|right|Isocost v. Isoquant Graph. Each line segment is an isocost line representing one particular level of total input costs, denoted TC in the graph and C in the article's text. PL is the unit price of labor (w in the text) and PK is the unit price of physical capital (r in the text).

In economics, an isocost line shows all combinations of inputs which cost the same total amount. Although similar to the budget constraint in consumer theory, the use of the isocost line pertains to cost-minimization in production, as opposed to utility-maximization. For the two production inputs labour and capital, with fixed unit costs of the inputs, the equation of the isocost line is rK+wL = C\,