<Dd> r K + w L = C (\ displaystyle rK + wL = C \,) </Dd> <P> where w represents the wage rate of labour, r represents the rental rate of capital, K is the amount of capital used, L is the amount of labour used, and C is the total cost of acquiring those quantities of the two inputs . </P> <P> The absolute value of the slope of the isocost line, with capital plotted vertically and labour plotted horizontally, equals the ratio of unit costs of labour and capital . The slope is: </P> <Dl> <Dd> − w / r . (\ displaystyle - w / r. \,) </Dd> </Dl>

The slope of the isocost line is determined by