WACC (Weighted Average Cost of Capital) Calculator
The Weighted-Average Cost of Capital (WACC) is the blended cost a firm pays its equity and debt investors — and the standard discount rate used in DCF valuation and NPV-based capital budgeting. Enter the market values of equity and debt, the cost of equity (typically from CAPM), the pre-tax cost of debt and the marginal tax rate to get WACC, the capital-structure weights and the after-tax cost of debt that incorporates the interest tax shield.
Enter valid numbers: E, D ≥ 0 with E + D > 0; Re, Rd, Tc between 0–100 %.
WACC
9.00%
Weighted-average cost of capital — the discount rate for DCF/NPV valuation and the minimum acceptable return for new projects.
Capital-structure breakdown
- Equity weight E ÷ V
- 60.0%
- Debt weight D ÷ V
- 40.0%
- After-tax cost of debt Rd · (1 − Tc)
- 4.50%
Interest is tax-deductible, so the effective cost of debt is multiplied by (1 − Tc). Equity dividends are not — this is the well-known "tax shield" on debt.
Formula
WACC = (E ÷ V)·Re + (D ÷ V)·Rd·(1 − Tc), where V = E + D
Use market values (not book) for E and D, and pair pre-tax Rd with the (1 − Tc) tax shield — consistent with Brealey, Myers & Allen, "Principles of Corporate Finance".
Formula
WACC = (E ÷ V)·Re + (D ÷ V)·Rd·(1 − Tc), where V = E + D After-tax cost of debt = Rd · (1 − Tc)
- · E and D should be at market value, not book value: for a listed firm, E = share price × shares outstanding; D should use market quotes for traded bonds (book value is an acceptable proxy for private firms).
- · The cost of equity Re is typically obtained from the CAPM: Re = Rf + β · (Rm − Rf), where Rf is the risk-free rate, β the equity beta and (Rm − Rf) the market risk premium.
- · Use the pre-tax cost of debt Rd; the interest tax shield is captured by the (1 − Tc) factor — interest is tax-deductible whereas equity dividends are not.
- · Common corporate income-tax rates (2024): Hong Kong 16.5 %, Singapore 17 %, UK 25 %, US federal 21 %, mainland China 25 %. In practice use the firm’s effective or marginal tax rate.
- · Common uses: (1) discount rate for DCF / NPV valuation; (2) capital budgeting — projects with IRR > WACC create value; (3) capital-structure decisions — find the D/E mix that minimises WACC.
- · Limitation: WACC assumes a stable capital structure. For deals with quickly changing leverage (e.g. leveraged buyouts), the Adjusted Present Value (APV) method is preferred.
- · References: Brealey, Myers & Allen, "Principles of Corporate Finance"; Aswath Damodaran, "Investment Valuation" — standard MBA and CFA texts.
Frequently asked
How does WACC relate to IRR and the required rate of return?
WACC is the firm’s "hurdle rate": projects with IRR > WACC return enough to cover the cost of capital and create shareholder value; projects with IRR < WACC should be rejected. It is also the discount rate used in NPV — when expected cash flows are discounted at WACC, NPV > 0 signals a value-creating project. For projects with above-average risk, raise WACC by 1–5 %; below-average risk projects warrant a lower discount rate.
Why use market values rather than book values for E and D?
WACC measures the cost of raising capital *today*, so it should use today’s market prices — new equity is issued at the current share price and new debt borrowed at current yields. Book values reflect historical cost and badly under-state equity weight for mature firms trading well above book (e.g. P/B > 3), biasing WACC toward the cheaper debt side. Damodaran and other standard texts uniformly recommend market values.
What is the tax shield and does every firm benefit from it?
Interest expense is tax-deductible, so the effective cost of debt is multiplied by (1 − Tc). Example: Rd = 6 %, Tc = 25 % → after-tax cost 4.5 %. The shield is reduced or lost when (a) the firm has no taxable income to shield (operating losses or NOL carry-forwards) or (b) the jurisdiction caps interest deductibility (e.g. US TCJA limit of 30 % of EBITDA). In those cases adjust WACC upward accordingly.
Can a firm lower its WACC simply by taking on more debt?
In the short run yes, because (1 − Tc)·Rd is usually below Re, so adding debt tilts the average toward the cheaper component. But once leverage gets too high, bankruptcy risk rises — bondholders demand higher Rd and shareholders demand higher Re (leverage raises the equity beta) — and WACC bends back up. There is therefore an "optimal capital structure," the core prediction of the Modigliani–Miller theorem (with-tax version).
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