βοΈ WACC Calculator
Your firm's blended hurdle rate.
WACC
Estimates for planning only, not financial advice.
Equity $650M, debt $350M, cost of equity 10 percent, cost of debt 5 percent, tax 21 percent: WACC is 7.88 percent. The equity leg contributes 6.50 points, the after-tax debt leg 1.38 points. Every project this firm takes must clear 7.88 percent to create value.
How to Use This Calculator
Enter market values of equity and debt, the cost of each, and the tax rate. The calculator weights them into the blended hurdle rate used for DCF and project decisions.
Enter market value of equity (market cap) and market value of debt, not book values.
Enter cost of equity (CAPM: risk-free + beta x market premium) and pre-tax cost of debt (current borrowing rate).
Use the result as the DCF discount rate and the minimum acceptable project return.
The Formula
Each capital source contributes its cost weighted by its share of firm value. Debt gets the (1 - tax) factor because interest is tax-deductible: the government subsidizes borrowing. More debt lowers WACC mechanically, which is why the formula alone seems to say "borrow infinitely"; bankruptcy risk, not the formula, is the limiter.
Worked Example
E = 650, D = 350, V = 1,000. Weights: 65 percent equity, 35 percent debt. After-tax debt cost: 5 x (1 - 0.21) = 3.95 percent. WACC: 0.65 x 10 + 0.35 x 3.95 = 6.50 + 1.3825 = 7.8825, shown as 7.88 percent. Shift to 50/50 weights and WACC falls to 6.98 percent; go all-equity and it is 10 percent. Capital structure moves the hurdle by whole points.
Estimating the Inputs
| Input | Standard approach |
|---|---|
| Cost of equity | CAPM: rf + beta x (market risk premium) |
| Beta | Bottom-up: unlever peers, relever at target D/E |
| Cost of debt | Current yield on the firm's bonds / borrowing rate |
| Weights | Market values; target structure, not today's accident |
| Tax rate | Marginal rate, not effective |
Use target weights, not today's: if the firm just paid down debt temporarily, weight at the long-run structure. For beta work, our unlevered beta calculator builds the bottom-up beta; for the cash flows to discount, the FCFF calculator.
Sensitivity and Judgment
WACC precision is an illusion: each input is an estimate, so report a range, not a point. Vary cost of equity by 1-2 points and watch valuation swing 15-25 percent; that sensitivity is the honest story. Common errors: book-value weights, stale debt costs from old bonds, using the effective tax rate, and forgetting that WACC assumes a constant capital structure while the forecast changes it. Get the structure roughly right and the rate roughly right; false precision helps no one.
WACC in the Real World: a Mini Case
Consider a mid-size manufacturer: $800 million market cap, $200 million in debt trading near par, so equity is 80 percent of capital and debt 20 percent. Its beta is 1.1; with a 4.5 percent risk-free rate and 5 percent market risk premium, CAPM gives cost of equity of 4.5 + 1.1 x 5 = 10 percent. Its bonds yield 6 percent, and the 21 percent tax rate makes after-tax cost of debt 6 x 0.79 = 4.74 percent. WACC = 0.80 x 10% + 0.20 x 4.74% = 8.95%.
Now watch the judgments hidden in that tidy number. The 80/20 weights use market values; book equity would have shown a different mix and a different WACC. The 1.1 beta came from a two-year regression with an R-squared of 0.35: reasonable, not gospel. The 5 percent market risk premium is a long-run historical average; using 4 or 6 percent moves WACC by 80 basis points either way, which swings a DCF valuation by double digits. Honest analysts present the valuation across a WACC range, because the point estimate is precise and wrong.
Private companies add layers: no observable beta (use unlevered peer betas, relevered at the target debt level), no market cap (use target capital structure), and usually a size premium of 2 to 4 percent on the cost of equity. Startups and distressed firms may warrant company-specific risk premiums on top. The formula never changes; the craftsmanship is all in the inputs, and the best WACC build is the one whose every assumption is written down and defensible.
The Hurdle That Rules Valuation
WACC is the hurdle rate for every corporate investment and the discount rate for every DCF. Build it from market-value weights, a CAPM cost of equity, and after-tax cost of debt; then stress-test it, because small input changes move valuations a lot. A carefully built 8.95 percent beats a sloppy 10 percent every time: in valuation, the discount rate is the model.
Small Inputs, Big Consequences
A one-point change in WACC typically moves a DCF valuation 10 to 15 percent, which is why the build deserves care disproportionate to its simplicity. Document every assumption, use market-value weights, and present valuations as ranges across plausible WACC values. Precision in the formula is easy; honesty about the inputs is the real skill.
Estimates for planning only, not financial advice.
Frequently Asked Questions
What is WACC?
Weighted Average Cost of Capital: the blended required return of all capital providers, weighting cost of equity and after-tax cost of debt by market-value shares. It is the standard discount rate for DCF valuations and the hurdle rate for projects.
How do you calculate WACC?
WACC = (E/V) x Re + (D/V) x Rd x (1-T). With $650M equity, $350M debt, 10% cost of equity, 5% cost of debt, 21% tax: 0.65x10 + 0.35x5x0.79 = 7.88%. Each input is observable or estimable: market cap for E, debt market value for D, CAPM for Re, bond yields for Rd, and the statutory rate for T.
Why is debt multiplied by (1 - tax rate)?
Because interest is tax-deductible: a 5% coupon at 21% tax costs the firm only 3.95% after the tax shield. This is the main mechanical reason debt lowers WACC. The government effectively subsidizes borrowing by letting interest reduce taxable income; equity dividends get no such shield, which is why the tax code favors debt financing.
Should I use book or market values?
Market values: market cap for equity, market (or book as proxy) for debt. Book equity is often stale and understates the equity weight for successful firms, which overstates WACC. For debt, book value usually approximates market value well since most corporate debt trades near par; the equity side is where book values mislead badly.
How do I estimate cost of equity?
CAPM: risk-free rate + beta x equity risk premium. US practitioners commonly use ~4.5-5.5% market risk premium and the 10-year Treasury as rf. Bottom-up betas (unlever peers, relever) beat single regressions. For private firms, add a size premium (2-4%) and possibly a company-specific risk premium; public-company CAPM alone understates small-firm risk.
What is the hurdle rate?
The minimum acceptable return on a project, usually WACC (or divisional WACC for conglomerates). Projects earning above WACC create value; below it destroy value. Riskier projects get risk-adjusted hurdle rates above WACC. Conglomerates should use divisional hurdle rates: applying a blended WACC lets risky divisions overinvest and starves safe ones of capital.
Does more debt always lower WACC?
In the formula, yes; in reality, no. Beyond moderate borrowing, debt costs rise, equity holders demand more for distress risk, and expected bankruptcy costs offset the tax shield. The trade-off theory optimum is well short of 100% debt. Empirical optima cluster around 20-40% debt for most industries; utilities sustain more, volatile tech firms less.
WACC vs cost of equity: when to use each?
WACC discounts unlevered cash flows (FCFF) to enterprise value. Cost of equity discounts levered cash flows (FCFE) to equity value directly. Match the cash flow to the rate; mixing them is the classic DCF error. Discounting FCFE at WACC understates value (too low a rate for equity risk); discounting FCFF at cost of equity overstates it. The pairing is the whole discipline.
How sensitive is valuation to WACC?
Very: a 1-point WACC change typically moves DCF value 15-25%. Always present valuation as a range over WACC scenarios rather than a single number from a point estimate. The sensitivity is highest for long-duration growth companies where most value sits in the terminal value; mature cash cows are less sensitive.
What tax rate goes in WACC?
The marginal corporate tax rate the firm faces on additional interest deductions (21% US federal plus state effects), not the historical effective rate. Loss-making firms with no taxable income get little shield value. Multinationals should use a blended rate reflecting where the debt and deductions actually sit, not just the headquarters' statutory rate.