Weighted Average Cost of Capital (WACC)
Weighted Average Cost of Capital (WACC) is the blended rate a company is expected to pay on average to all its capital providers — debt holders and equity holders — weighted by the proportion each source represents in the total capital structure.
WACC serves as the foundational discount rate in discounted cash flow (DCF) analysis. When an analyst projects future free cash flows for a company like Apple or ExxonMobil, those future dollars must be discounted back to today's value, and WACC is the rate applied to perform that discounting. A higher WACC compresses valuations; a lower WACC inflates them, which is why small changes in the WACC assumption can swing a DCF valuation by hundreds of millions of dollars.
The formula brings together two costs: the cost of equity and the after-tax cost of debt, each weighted by its share of total capital. Expressed formally: WACC = (E / V) x Re + (D / V) x Rd x (1 - Tc), where E is the market value of equity, D is the market value of debt, V = E + D is total capital, Re is the cost of equity, Rd is the cost of debt, and Tc is the corporate tax rate. The (1 - Tc) term reflects the tax shield on interest payments: because interest is deductible, the government effectively subsidizes debt financing.
Consider a mid-cap US manufacturer with a capital structure that is 60% equity (cost of equity 10%) and 40% debt (pre-tax cost of debt 5%) paying a 21% federal corporate tax rate. WACC = 0.60 x 10% + 0.40 x 5% x (1 - 0.21) = 6% + 1.58% = 7.58%. Every projected free cash flow is discounted at 7.58% per year.
Determining the inputs is where judgment enters. The cost of equity is typically estimated via the Capital Asset Pricing Model (CAPM), using the risk-free rate (commonly the 10-year US Treasury yield), a beta measuring the stock's systematic risk, and an equity risk premium. The cost of debt is observable from outstanding bond yields or recent borrowing rates. Analysts must also decide whether to use book-value or market-value weights — finance theory favors market values.
WACC is sensitive to capital-structure changes, interest-rate environments, and shifts in market beta. A leveraged buyout that loads a firm with debt initially lowers WACC via the tax shield but raises financial distress risk, which can push up both Re and Rd over time. Investors modeling US companies should cross-check their WACC against industry benchmarks from sources like Damodaran's annual estimates to ensure the assumption is grounded in observable market data.