WACC refers to the weighted average cost of capital, while MCC refers to the marginal cost of capital.
The marginal cost of capital is a concept that refers to the weighted average cost of the last $1 raised in a business. The concept is used in capital budgeting. On the other hand, the weighted average cost of capital is a calculation of a firm's cost of capital in each category of capital. While WACC refers to total capital, or to the capital of a given project, MCC refers only to the average cost of the last portion of capital raised.
