Weighted Average Cost of Capital

Why weighted average cost of capital matters

WACC connects financing risk with enterprise valuation and capital budgeting. A business creates value when returns on incremental invested capital exceed an appropriate cost of capital. Because discount rates strongly affect long-duration cash flows, modest WACC changes can materially alter modeled value. The measure should reflect the target capital structure and risk of the cash flows, not simply the company’s current borrowing coupon.

How it is applied

Estimate cost of equity using a risk-free rate, beta, and equity risk premium or another suitable model. Estimate marginal pre-tax borrowing cost from current market evidence, then apply the tax shield when interest is deductible. Weight debt and equity by market value under a sustainable target structure. Additional capital classes can be included. Currency, inflation, leverage, country risk, and forecast cash-flow definition must remain consistent.

Formula

Portfolio example

A company is financed with 70% equity and 30% debt by market value. Cost of equity is 10%, pre-tax debt cost 6%, and tax rate 25%. WACC is about 8.35%. Discounting firm cash flow at 6% would overvalue the business by treating debt cost as though it applied to all capital and ignoring equity risk.

How to interpret it

Higher WACC lowers present value and indicates greater required compensation. A project should use a rate matching its own risk rather than automatically using the corporate average. Falling WACC can reflect lower market rates or risk, but adding debt does not reduce it indefinitely because financial risk raises both debt and equity costs. Sensitivity ranges should show how much valuation depends on the estimate.

Limitations and common misconceptions

Beta, equity premium, target leverage, debt cost, and tax shield are uncertain. Book-value weights are a common error. A constant WACC can be inappropriate when leverage or risk changes through time, and private-company estimates need judgment. Country, currency, and distress risks may be double-counted. WACC is not suitable for cash flows to equity or contractual debt cash flows without careful analytical adjustment, testing, and reconciliation.