WACC Calculator — Cost of Equity & Debt

Calculate the Weighted Average Cost of Capital (WACC) from cost of equity, after-tax cost of debt, and market-value weights. The discount rate for valuing projects.

Equity Market Value ($)
Debt Market Value ($)
Cost of Equity (%)
Cost of Debt (%)
Corporate Tax Rate (%)
0.06%
Weighted Average Cost of Capital on a total capital base of $1,000,000
Weighted component breakdown
ComponentWeightCostContribution
Equity60.00%8.00%4.80%
Debt (after tax)40.00%4.00%(1−T)1.60%
WACC0.06%
Equity weight 60.00% × cost of equity 8.00% + debt weight 40.00% × after-tax cost of debt 4.00%
WACC formula: WACC = (E/V × Re) + (D/V × Rd × (1 − T)), where V = E + D. The debt component is multiplied by (1 − T) to reflect the tax deductibility of interest — the Modigliani-Miller tax shield. Results are illustrative and not financial advice.

What Is WACC and Why It Matters

The Weighted Average Cost of Capital (WACC) is the blended rate a company must earn on its existing assets to satisfy all of its capital providers — both shareholders and lenders. It is the discount rate most commonly used to value a firm's future cash flows in a discounted cash flow (DCF) analysis, and it is the hurdle rate against which new investment projects are judged. If a project returns more than the WACC, it creates value for shareholders; if it returns less, it destroys value even when it is profitable in an accounting sense.

The formula weights the cost of each source of capital by its share of the total capital structure. Equity is weighted by E/V, the market value of equity divided by total value, and debt by D/V. Because interest payments are tax-deductible, the cost of debt is reduced by the corporate tax rate through the (1 − T) term — this is the Modigliani-Miller tax shield. The result is a single percentage that reflects both the risk of the firm's operations and the mix of financing used to fund them.

Reading the Weighted Component Breakdown

The breakdown table above shows how each source of capital contributes to the final WACC. The equity contribution is its weight multiplied by the cost of equity, while the debt contribution uses the after-tax cost of debt. In the default example, equity contributes 4.80% and debt contributes 1.60%, summing to a 6.40% WACC. Notice that debt is cheaper than equity both because lenders demand a lower return and because of the tax shield — which is why adding debt lowers WACC up to the point where financial distress costs begin to outweigh the benefit.

Practical Considerations

Market values, not book values, should be used for both equity and debt, because WACC reflects the opportunity cost to current investors. The cost of equity is typically estimated with the Capital Asset Pricing Model (CAPM), and the cost of debt with the yield on the company's existing bonds. WACC is sensitive to its inputs — a small change in the cost of equity or the tax rate can move the result by tens of basis points — so it is best treated as a range rather than a precise number, and stress-tested across reasonable scenarios before being used to make investment decisions.

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The Weighted Average Cost of Capital (WACC) is the blended rate a company pays to finance its operations through a mix of equity and debt. It is the single most important discount rate in corporate finance because it represents the minimum return a company must earn on its investments to satisfy every provider of capital. When a project's expected return exceeds WACC, it creates value; when it falls short, it destroys value.

The building blocks of WACC

WACC is built from four inputs. The cost of equity is the return shareholders require, most often estimated with the Capital Asset Pricing Model (CAPM): Re = Rf + β × (Rm − Rf). The cost of debt is the interest rate a company pays on its borrowings, and because interest is tax-deductible it is multiplied by (1 − Tc) to capture the tax shield. The weights are the market values of equity and debt as a share of total capital. The formula is WACC = (E/V × Re) + (D/V × Rd × (1 − Tc)).

Why the tax shield matters

Debt is cheaper than equity for two reasons: lenders accept a lower return because their claim is senior, and interest payments reduce taxable income. The (1 − Tc) term captures this second effect. A company with a 25% tax rate and a 6% pre-tax cost of debt effectively pays only 4.5% after tax. This is why adding debt lowers WACC up to a point — but only up to the point where financial distress risk and a rising equity risk premium outweigh the tax benefit.

Using WACC in valuation

WACC is the discount rate in discounted cash flow (DCF) analysis. You project a company's free cash flows and discount them back at WACC to arrive at enterprise value. It is also the hurdle rate for capital budgeting: a project with an internal rate of return above WACC is worth pursuing. Because WACC depends on market values and current rates, it is a moving target that should be recomputed as capital structure and market conditions change.

Practical guidance

Use market values, not book values, for the equity and debt weights. Estimate the cost of equity with a beta that reflects the company's true systematic risk, and use a forward-looking risk-free rate. For a private company, use a comparable public company's beta or an industry average. The result is an estimate, not a precise number — sensitivity analysis around the inputs is always wise before making a large capital decision.

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