What Is the Cost of Debt in WACC

Title: What Is the Cost of Debt in WACC: Understanding the Importance and Calculation


Determining the weighted average cost of capital (WACC) is crucial for businesses to make informed financial decisions. It provides a comprehensive view of the cost of financing a company’s operations and investments. A significant component of WACC is the cost of debt, which represents the expense of borrowing funds. This article delves into the concept of the cost of debt in WACC, its significance, and how to calculate it accurately.

Understanding the Cost of Debt:

The cost of debt is the interest rate a company pays on its borrowings. It is the return expected by lenders for providing funds to the business. Debt can be in the form of bank loans, bonds, or other financial instruments. Unlike equity, debt comes with a predetermined interest rate, which makes its calculation relatively straightforward.

Significance of the Cost of Debt in WACC:

1. Reduces WACC: Including debt in the capital structure allows companies to benefit from the tax-deductible interest payments. As interest expenses lower the taxable income, the effective cost of debt reduces, consequently lowering the overall WACC.

2. Shows Risk Profile: The cost of debt reflects a company’s creditworthiness. Higher interest rates are associated with greater risk, indicating that the company may have difficulty repaying its obligations. Creditors and investors use this information to assess the financial health and stability of the business.

3. Balances Capital Structure: The cost of debt helps in maintaining an optimal capital structure by balancing the proportion of debt and equity. By comparing the cost of debt with the cost of equity, companies can determine the right mix of financing to minimize the WACC and maximize shareholder value.

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Calculating the Cost of Debt:

The cost of debt can be calculated through the following steps:

1. Identify the Interest Rate: Determine the interest rate the company is paying on its debt. This can be obtained from loan agreements or by analyzing interest expenses in the financial statements.

2. Adjust for Taxes: As interest paid on debt is tax-deductible, the cost of debt should be adjusted to reflect the tax shield. Multiply the interest rate by (1 – Tax Rate) to factor in the tax benefits.

3. Weight the Cost: The proportion of debt in the company’s capital structure must be considered. Multiply the adjusted cost of debt by the debt weight (debt ÷ total capital) to obtain the weighted cost of debt.


Q1. Why is the cost of debt important in WACC calculation?
A1. The cost of debt represents the expense associated with borrowing funds, and including it in the WACC calculation provides a holistic view of the company’s cost of capital.

Q2. How does the cost of debt affect a company’s risk profile?
A2. Higher interest rates indicate higher risk, as it implies that lenders expect a higher return due to the perceived risks associated with the company’s ability to repay its obligations.

Q3. Can the cost of debt change over time?
A3. Yes, the cost of debt can change due to various factors such as market conditions, credit ratings, and changes in the company’s financial health. It is important to regularly reassess the cost of debt to ensure accurate WACC calculations.

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Q4. What are some common sources of debt for businesses?
A4. Businesses can obtain debt from sources such as bank loans, lines of credit, bonds, or debentures. The interest rates can vary depending on the type of debt instrument and the company’s creditworthiness.


Understanding the cost of debt in the WACC calculation is crucial for businesses to make informed financial decisions. By including the cost of debt, companies can determine the optimal capital structure, balance risk, and reduce the overall cost of capital. Accurately calculating the cost of debt by considering the interest rate, tax shield, and debt weight is essential for maintaining a realistic representation of the cost of financing.