Capital Structure Considerations
The Marginal Cost of Capital
The marginal cost of capital is
calculated as the cost of the last dollar of capital raised. Generally, as capital is raised, the marginal cost of
capital rises. This happens because the marginal cost of capital is generally the weighted average
of the cost of raising the last dollar of capital.
When raising extra capital, firms usually try to stick to the desired capital structure. Once sources are depleted, they will usually have to issue more equity. Since the cost of issuing extra equity seems to be higher
than other financing costs, we see an increase in the marginal cost of
capital as the amounts of capital raised grow higher.

Cost of Money The Marginal Cost of Capital is the cost of the last dollar of capital raised. The firm should consider this when making corporate decisions.
The marginal cost of capital can also be discussed as the
minimum acceptable rate of return or hurdle rate. Capital investment is logically only a good decision if the return on the capital
is greater than its cost. Also, a negative return is generally
undesirable. As a result, the marginal cost of capital often becomes a
benchmark number in the decision-making process to raise more capital. If it is determined that the dollars invested in raising
this extra capital could be allocated toward a greater or safer return
if used differently, according to the firm, they will be directed
elsewhere. For this, we must look into marginal returns of capital, which can be described as the gains or returns made by raising that last
dollar of capital.
Key Points
- The marginal cost of capital is calculated as being the cost of the last dollar of capital raised.
- When raising extra capital, firms will try to stick to their desired capital structure, but once sources are depleted, they will have to issue more equity. Since this tends to be higher than other sources of financing, we see an increase in the marginal cost of capital as capital levels increase.
- Since a capital investment is logically only a good decision if the return on the capital is greater than its cost, and a negative return is generally undesirable, the marginal cost of capital often becomes a benchmark number in the decision-making process that goes into raising more capital.
Terms
- Capital Gains Yield – compound rate of return of increases in a stock's price
- Marginal Tax Rate – the percent paid out to the government of the last dollar (or applicable currency) earned
- Marginal Cost of Capital – the cost of the last dollar of capital raised or the minimum acceptable rate of return or hurdle rate.