What is WACC and how do you calculate it?

WACC (Weighted Average Cost of Capital) is the blended rate of return required by all capital providers. It's calculated as: Cost of Equity × (E/V) + Cost of Debt × (1-Tax Rate) × (D/V), where E is equity value, D is debt value, and V is total value.

Expected Time

1-2 minutes

Difficulty

Medium

Frequency

Very Common

Why Interviewers Ask This

WACC is the discount rate used in DCF analysis, making it fundamental to valuation work. Interviewers want to ensure you understand how companies are financed and why different sources of capital have different costs. This question also tests your knowledge of CAPM and capital structure.

How to Structure Your Answer

First define WACC and its purpose. Then walk through the formula component by component. Explain how to calculate cost of equity using CAPM, how to find cost of debt, and why we use market values for weights.

Key Points to Cover

WACC = (E/V) × Re + (D/V) × Rd × (1-T)
Cost of Equity (Re) calculated using CAPM: Rf + β × (Rm - Rf)
Cost of Debt (Rd) is the yield on the company's debt or comparable debt
Debt is tax-deductible, hence the (1-T) term
Use market values for weights, not book values
WACC represents the minimum return needed to satisfy all investors

Sample Answer

WACC, or Weighted Average Cost of Capital, represents the blended rate of return that a company must earn to satisfy all of its capital providers - both debt holders and equity holders. It's the discount rate we use in DCF analysis to present-value future cash flows.

The formula is: WACC equals the weight of equity times the cost of equity, plus the weight of debt times the after-tax cost of debt.

Let me break down each component:

First, the cost of equity is typically calculated using CAPM - the Capital Asset Pricing Model. That's the risk-free rate plus beta times the equity risk premium. The risk-free rate is usually the 10-year Treasury yield. Beta measures the stock's volatility relative to the market. The equity risk premium is typically 5-7%.

Second, the cost of debt is the yield the company pays on its debt. For public companies, you can look at the yield on their traded bonds. We multiply by one minus the tax rate because interest is tax-deductible - the government effectively subsidizes part of the interest cost.

Third, for the weights, we use market values rather than book values. Equity weight is market cap divided by total enterprise value. Debt weight is market value of debt divided by enterprise value.

As an example, if a company has a 10% cost of equity, 5% pre-tax cost of debt, a 25% tax rate, and is 70% equity and 30% debt, the WACC would be: 70% × 10% + 30% × 5% × (1-25%) = 7% + 1.125% = 8.125%.

A lower WACC increases DCF valuations because you're discounting at a lower rate, making future cash flows more valuable today.

Common Mistakes to Avoid

Forgetting to tax-affect the cost of debt
Using book values instead of market values for weights
Not knowing the CAPM formula for cost of equity
Confusing WACC with cost of equity

Pro Tip

If asked why debt is cheaper than equity, explain that debt holders have priority in bankruptcy and receive contractual payments, making it less risky than equity, which has residual claims and uncertain returns.