How to Calculate WACC Step by Step: A Worked Example With Every Formula Explained

WACC (Weighted Average Cost of Capital) is the blended cost of a company's financing — the minimum return the company must earn on its existing assets to satisfy its creditors and shareholders. The formula: WACC = (E/V) × Re + (D/V) × Rd × (1 - T) Where: E = market value of equity, D = market value of debt, V = E + D (total firm value), Re = cost of equity, Rd = cost of debt, T = corporate tax rate. The (1 - T) tax adjustment on debt is critical and frequently forgotten on exams. Interest payments on debt are tax-deductible — if a company pays 6% interest and its tax rate is 25%, the after-tax cost of that debt is 6% × (1 - 0.25) = 4.5%. The government effectively subsidizes the interest expense through the tax deduction. Equity has no such tax benefit — dividends are not tax-deductible. Worked example — we will calculate WACC for a company with: 10 million shares outstanding at $50/share, $150 million in bonds with YTM of 6%, equity beta of 1.2, risk-free rate of 4%, market risk premium of 6%, and a 25% tax rate. Snap a photo of any WACC problem and FinanceIQ walks through each component step by step — Re via CAPM, after-tax Rd, market weights, and the final WACC. This content is for educational purposes only and does not constitute financial advice.

The Capital Asset Pricing Model: Re = Rf + β × (Rm - Rf) Where: Rf = risk-free rate (typically the 10-year Treasury yield), β = equity beta (measures the stock's volatility relative to the market), (Rm - Rf) = market risk premium (expected market return minus the risk-free rate). For our example: Rf = 4%, β = 1.2, market risk premium = 6%. Re = 4% + 1.2 × 6% = 4% + 7.2% = 11.2%. Interpretation: equity investors in this company require an 11.2% return to compensate for the risk of holding the stock. The beta of 1.2 means the stock is 20% more volatile than the market — so investors demand a premium above the market return. Common mistakes: using the total market return instead of the market risk premium (if the question says expected market return is 10% and risk-free is 4%, the MRP is 6%, not 10%), using the wrong risk-free rate (match the maturity to the investment horizon — 10-year Treasury for most WACC calculations, not the 3-month T-bill), and confusing levered and unlevered beta (use the company's actual levered beta for WACC — unlevered beta is for comparable company analysis). FinanceIQ identifies which form of CAPM a problem requires and solves it step by step — whether the question gives you the market return, the MRP, or asks you to calculate one from the other.

Cost of debt = YTM × (1 - T). The yield to maturity (YTM) on the company's bonds is the best measure of current debt cost — not the coupon rate (which reflects the rate when the bonds were issued, possibly years ago). For our example: Bond YTM = 6%, Tax rate = 25%. After-tax Rd = 6% × (1 - 0.25) = 6% × 0.75 = 4.5%. Market value of equity: E = shares outstanding × share price = 10 million × $50 = $500 million. Market value of debt: D = $150 million (in practice, this is the market price of the bonds, not the face value — but many textbook problems give you the market value directly or use face value as an approximation). Total firm value: V = E + D = $500M + $150M = $650 million. Weights: E/V = $500M / $650M = 76.9%. D/V = $150M / $650M = 23.1%. These must add to 100%. The most common weight mistake: using book values instead of market values. A company whose stock has tripled since it was issued has much higher market equity than book equity. Using book values underweights equity and overweights debt, producing a WACC that is too low. Exams almost always specify whether to use market or book — if unspecified, use market values.

WACC = (E/V) × Re + (D/V) × Rd × (1-T) WACC = (0.769 × 11.2%) + (0.231 × 4.5%) WACC = 8.61% + 1.04% WACC = 9.65% Interpretation: this company's blended cost of capital is 9.65%. Any project the company undertakes must earn at least 9.65% to create value for shareholders. Projects with expected returns above 9.65% increase firm value (positive NPV). Projects below 9.65% destroy value. Notice: the equity component (8.61%) dominates because equity is both a larger proportion of the capital structure (76.9%) and more expensive (11.2% vs 4.5% after-tax). This is always true — equity is more expensive than debt because equity holders bear more risk (they are last in line for claims on the company's assets). Sanity check: WACC should always fall between the after-tax cost of debt (4.5%) and the cost of equity (11.2%). If your calculated WACC is outside this range, you made an arithmetic error. This sanity check catches mistakes on exams instantly. What changes WACC: increasing leverage (more debt, less equity) generally decreases WACC because debt is cheaper than equity — but only up to a point. Beyond an optimal debt level, the increased financial risk raises both the cost of debt and the cost of equity, and WACC starts increasing again. This is the trade-off theory of capital structure. FinanceIQ solves WACC problems from any starting point — whether the question gives you CAPM inputs, bond data, or asks you to work backward from a target WACC to find the maximum acceptable cost of equity.