Calculating WACC

Introduction

In our recent lessons, we have systematically built the toolkit needed to determine the cost of a company's financing. We started by estimating the cost of equity ( $K_{e}$ ) using both CAPM and the Dividend Growth Model, and then in our last session, we focused on calculating the after-tax cost of debt ( $K_{d}$ ). Now, we will integrate these individual components to derive one of the most crucial metrics in corporate finance.

This lesson is dedicated to achieving the learning outcome: Calculate the weighted average cost of capital (WACC). The WACC represents the blended, average cost a company pays for its funds from all sources—equity holders and lenders. It is the minimum return a company must earn on its existing asset base to satisfy its creditors and owners. As such, it's a fundamental benchmark, or "hurdle rate," for evaluating new projects and a key input for valuing the entire business.

We will start by cementing the concept of a weighted average, then introduce the formula, and finally, work through a comprehensive calculation.

1. Understanding the Weighted Average Cost of Capital

A company’s capital structure is its mix of financing, typically some combination of equity and debt. Each of these components has a different cost. Equity is generally more expensive than debt because equity investors bear more risk and demand a higher return. Debt is cheaper, especially after accounting for the tax deductibility of interest payments.

The WACC combines these different costs into a single, representative rate. It does this by weighting the cost of each capital source according to its proportion in the company's total capital structure. Since you have a background in statistics, the concept of a weighted average should be quite familiar. It's conceptually identical to calculating a weighted mean, where each component's cost is weighted by its relative importance (i.e., its market value).

This visual breakdown illustrates how the two main components, the cost of equity and the after-tax cost of debt, are combined to form the WACC.

This diagram shows the components of the Weighted Average Cost of Capital, combining the Cost of Equity and the Cost of Debt.

To start, let's watch a short video that provides an excellent conceptual overview of WACC and demonstrates with a simple example why this weighting is so important.

Cost of Capital (WACC)

This video from Kaplan UK introduces the concept of WACC and explains the logic behind the weighting process.

Watch the initial segment from the beginning. Focus on how the narrator explains WACC as an average cost and why a simple average is insufficient. The pie chart and the subsequent calculation clearly illustrate how the final WACC is influenced more heavily by the component with the larger proportion in the capital structure.

2. The WACC Formula and Its Components

Now that we have the conceptual foundation, let's look at the formula itself. The WACC is calculated by summing the weighted cost of each capital component. For a company financed by equity and debt, the formula is:

WACC = (\frac{E}{V}) \times R_{e} + (\frac{D}{V}) \times R_{d} \times (1 - T_{c})

Where:

$E$ = Market value of the company's equity
$D$ = Market value of the company's debt
$V$ = Total market value of the company's capital ( $E + D$ )
$R_{e}$ = Cost of equity (the $K_{e}$ we calculated in previous lessons)
$R_{d}$ = Before-tax cost of debt (the $K_{d b}$ from our last lesson)
$T_{c}$ = Corporate tax rate

The terms $\frac{E}{V}$ and $\frac{D}{V}$ are the weights of equity and debt in the total capital structure.

For a more detailed breakdown of this formula, please review the following text.

Weighted Average Cost of Capital (WACC): Formula and ... - CLFI

This resource from CLFI provides a clear, formal presentation of the WACC formula and defines each variable.

Read the section under the heading The WACC Formula. Pay close attention to the table that defines each variable (E, D, V, Re, Rd, Tc). This section solidifies the formula we will be using.

A Crucial Point: Market Value vs. Book Value

One of the most important aspects of calculating WACC, and a common area for mistakes, is the use of market values for the weights, not book values.

Book values (what you see on the Statement of Financial Position) are historical costs and may not reflect the current economic reality.
Market values (market capitalisation for equity, current market price for debt) represent the current prices at which the company's securities are trading. They reflect the market's perception of the value of future cash flows and are the relevant figures for assessing the cost of raising new capital today.

The following reading explains this distinction clearly.

Weighted Average Cost of Capital (WACC): Formula and ... - CLFI

This section explains why using market value weights is essential for an accurate WACC calculation.

Please read the section titled Determining Capital Structure Weights. This explains why book values can be misleading and how to determine the market values for both equity and debt.

3. Calculating WACC: A Step-by-Step Worked Example

With the formula and its components understood, let's walk through a full calculation. The process can be broken down into three logical steps:

Calculate the costs of the individual components: Determine the cost of equity ( $R_{e}$ ) and the after-tax cost of debt ( $R_{d} \times (1 - T_{c})$ ). In an exam question, these might be given or you might have to calculate them using methods from our previous lessons (e.g., CAPM for $R_{e}$ , IRR for $R_{d}$ ).
Determine the market value weights: Calculate the market value of equity ( $E$ ) and debt ( $D$ ), find the total value ( $V = E + D$ ), and then compute the weights ( $E / V$ and $D / V$ ).
Combine the components: Insert the costs and weights into the WACC formula to find the final figure.

The following resource provides a perfectly structured, step-by-step example of this process.

Weighted Average Cost of Capital (WACC): Formula and ... - CLFI

This worked example for a hypothetical company, "Meridian Components plc," brings all the elements of the WACC calculation together.

Carefully study the section Worked Example. The table clearly lays out all the inputs—market values, costs, and the tax rate. Follow the calculations for: The weights of equity and debt (E/V and D/V). The cost of equity (Re) using the CAPM formula (a good refresher!). The after-tax cost of debt. The final WACC calculation, which combines these weighted components.

4. Practice Problem

Now it's your turn to apply what you've learned. The following problem is adapted from a CB1 specimen paper and tests the core principles of WACC calculation, especially the use of market values.

Scenario: Company J is a quoted retailer. This information relates to its current finances:

Cost of Finance	Book Value	Market Value
Equity	24.0%	$90 million
Borrowings	10.0%	$30 million

Company J pays corporation tax at a rate of 28%.

Question: What is Company J’s weighted average cost of capital (WACC)?

Take a few minutes to solve this on your own before revealing the solution.

Click here for the step-by-step solution

Step 1: Determine Market Value Weights

Market Value of Equity (E) = $90 million
Market Value of Debt (D) = $30 million
Total Market Value of Capital (V) = E + D = $90m + $30m = $120 million
Weight of Equity ( $E / V$ ) = $90m / $120m = 0.75 or 75%
Weight of Debt ( $D / V$ ) = $30m / $120m = 0.25 or 25%
(Note: The book values are distractors and are not used in the calculation).

Step 2: Calculate Component Costs

Cost of Equity ( $R_{e}$ ) = 24.0% (given)
Before-tax Cost of Debt ( $R_{d}$ ) = 10.0% (given)
Corporate Tax Rate ( $T_{c}$ ) = 28% (given)
After-tax Cost of Debt = $R_{d} \times (1 - T_{c}) = 10.0% \times (1 - 0.28) = 10.0% \times 0.72 = 7.2%$

Step 3: Calculate WACC

WACC = ( $E / V$ $\times$ $R_{e}$ ) + ( $D / V$ $\times$ After-tax Cost of Debt)
WACC = (0.75 $\times$ 24.0%) + (0.25 $\times$ 7.2%)
WACC = 18.0% + 1.8%
WACC = 19.8%

Conclusion

Today we have successfully combined the costs of equity and debt into the Weighted Average Cost of Capital. This composite metric provides a comprehensive measure of a company's cost of financing and is a cornerstone of modern finance.

Key Takeaways:

The WACC is the blended cost of a company's capital, reflecting the required return for both equity and debt holders.
The formula is: $WACC = (\frac{E}{V}) \times R_{e} + (\frac{D}{V}) \times R_{d} \times (1 - T_{c})$ .
It is crucial to use market values to determine the weights ( $E / V$ and $D / V$ ), as they reflect the current economic value of the financing sources.
The cost of debt must be adjusted for the tax shield, so the after-tax cost of debt is used in the formula.

Having established how to calculate WACC, a natural next question arises: can a company change its WACC by changing its mix of debt and equity? In our next lesson, we will explore this question by examining the famous Modigliani-Miller propositions, which provide a theoretical framework for understanding the relationship between a company's capital structure, its value, and its WACC.

Recommended resources

Introduction

1. Understanding the Weighted Average Cost of Capital

2. The WACC Formula and Its Components

A Crucial Point: Market Value vs. Book Value

3. Calculating WACC: A Step-by-Step Worked Example

4. Practice Problem

Conclusion