WACC Calculator — Weighted Average Cost of Capital

What This Calculator Does

This WACC calculator estimates the weighted average cost of capital for a company given its capital structure, cost of equity, cost of debt, and corporate tax rate. WACC is the discount rate used in discounted cash flow (DCF) valuation, capital budgeting, and firm comparisons. The calculator supports CAPM-based cost of equity (Re = Rf + β × ERP) and a manual override, so analysts can use either academic inputs or a custom hurdle rate.

WACC Formula

The standard formula blends the required return of equity holders and debt holders, weighted by their share of total capital, with debt adjusted for the interest tax shield:

WACC = (E/V × Re) + (D/V × Rd × (1 - T))

E: market value of equity
D: market value of debt
V = E + D: total capital
Re: cost of equity (from CAPM or manual)
Rd: pre-tax cost of debt
T: marginal corporate tax rate

Cost of Equity via CAPM

The Capital Asset Pricing Model estimates the required return on equity as: Re = Rf + β × (Rm - Rf). Rf is the risk-free rate (commonly the 10-year Treasury yield), β (beta) measures the stock's sensitivity to market returns, and (Rm - Rf) is the equity risk premium, typically 4% to 6% for developed markets. A beta above 1 indicates higher-than-market risk; below 1 indicates lower volatility relative to the market.

Worked Example

Suppose a firm has E = $1,000M, D = $400M, Rf = 4.25%, β = 1.10, ERP = 5.5%, Rd = 5.5%, and T = 25%:

Re = 4.25% + 1.10 × 5.5% = 10.30%
After-tax Rd = 5.5% × (1 - 0.25) = 4.125%
Weight of equity = 1,000 / 1,400 = 71.43%
Weight of debt = 400 / 1,400 = 28.57%
WACC = 0.7143 × 10.30% + 0.2857 × 4.125% ≈ 8.54%

How to Use WACC

DCF valuation: discount unlevered free cash flows (FCFF) at WACC.
Capital budgeting: a project's IRR must exceed WACC to add value.
Comparables analysis: WACC differences explain divergent valuations across peers.
Capital structure decisions: a target WACC guides leverage and refinancing choices.

Limitations and Caveats

WACC assumes a stable capital structure and constant risk. It struggles with distressed firms, early-stage companies, or those with complex securities (preferred stock, convertibles, warrants). For private companies, beta is often regressed from a peer set. For cross-border analysis, country risk premiums can be added to ERP. A single point WACC is a simplification; sophisticated models use a term structure of discount rates.

Sources and References

Damodaran, A. Investment Valuation (3rd Edition).
Ross, S. A., Westerfield, R. W., & Jaffe, J. Corporate Finance.
Modigliani, F. & Miller, M. “The Cost of Capital, Corporation Finance and the Theory of Investment.” American Economic Review, 1958.
Damodaran Online — country risk premiums and ERP datasets (NYU Stern).

Frequently Asked Questions

What is WACC?

WACC stands for Weighted Average Cost of Capital. It represents the average rate a company is expected to pay to finance its assets, weighted by the proportion of equity and debt in its capital structure. Investors and analysts use WACC as a discount rate in DCF valuation, capital budgeting decisions, and firm valuation comparisons.

How is WACC calculated?

WACC = (E/V × Re) + (D/V × Rd × (1 - T)). E is the market value of equity, D is the market value of debt, V = E + D, Re is the cost of equity, Rd is the pre-tax cost of debt, and T is the marginal corporate tax rate. The (1 - T) factor adjusts debt for the tax shield of interest expense.

Should I use book value or market value?

Always use market values when available. Market values reflect current investor expectations and the actual cost of raising new capital. Book values are accounting measures that lag market conditions and tend to understate the true cost of equity for growing companies. When market value of equity is not directly observable, you can approximate it as share price × diluted shares outstanding.

What is a good WACC value?

WACC varies significantly by industry, capital structure, and country risk. Mature US large-caps typically fall between 7% and 10%. Capital-intensive utilities and infrastructure often sit at 5% to 7%. High-growth, asset-light software or biotech firms can exceed 10% to 12% because their cost of equity is higher. WACC is a hurdle rate, so a project's expected return must exceed it to create value.

How do I find the cost of equity?

The most common approach is the Capital Asset Pricing Model (CAPM): Re = Rf + β × (Rm - Rf). Rf is the risk-free rate (often 10-year Treasury yield), β is the stock's beta versus the broad market, and (Rm - Rf) is the equity risk premium, typically 4% to 6% for US equities. You can enter a custom cost of equity directly or use the CAPM inputs in this calculator.

Why is debt cost reduced by the tax rate?

Interest expense is tax-deductible in most jurisdictions, which lowers the effective cost of debt. Multiplying cost of debt by (1 - T) captures the tax shield. A 6% pre-tax cost of debt at a 25% tax rate gives an after-tax cost of 4.5%. Some analyses use effective tax rate instead of marginal; use the rate that reflects taxes actually paid on the interest.

Can WACC be used as a discount rate?

Yes. WACC is the standard discount rate for free cash flow to firm (FCFF) valuations. It is the appropriate rate for unlevered cash flows because it represents the blended required return of all capital providers. For free cash flow to equity (FCFE), use cost of equity (Re) instead, since those cash flows belong to shareholders only.

What if my company has no debt?

If D = 0, the debt weight is zero and WACC equals cost of equity. This often happens for early-stage or asset-light businesses. In that case, the tax shield has no effect, and the calculator simply returns Re. Some analysts still include operating lease debt or convertible debt to capture hidden leverage.