What Is WACC? Weighted Average Cost of Capital Formula

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Weighted average cost of capital (WACC) is the average rate of return a company must pay to the providers of its capital, with each source of financing (common equity, debt and, where present, preferred stock) weighted by its share of the company’s total capital. Debt enters at its after-tax cost because interest is generally tax-deductible. The result is a single percentage that represents the minimum return the business has to earn on its existing asset base to satisfy both its lenders and its shareholders.

In valuation, WACC is the standard discount rate for a company’s free cash flows. In corporate finance, it serves as a hurdle rate for projects and acquisitions that carry roughly the same risk as the company as a whole.

What WACC represents

A company raises money from two broad groups. Lenders and bondholders provide debt and receive contractual interest. Shareholders provide equity and expect dividends and share price gains, although the company owes them no fixed amount. Each group has a required return, and from the company’s side, that return is a cost.

With a single source of financing, the cost of capital is simply the cost of that source. An all-equity company whose shareholders expect 10% a year has a cost of capital of 10%. A company funded only by bonds yielding 5% has a pre-tax cost of 5% and an after-tax cost of 5% × (1 - tax rate), because the interest reduces taxable income.

Most companies use a mix, so WACC asks: across every dollar of capital the company has raised, what return do its suppliers require on average? It is an opportunity cost. Investors could buy other securities of similar risk, so the company has to offer at least what those alternatives would pay.

The WACC formula

The standard two-source formula is:

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

where:

• E = market value of the company’s equity
• D = market value of the company’s debt
• V = E + D, the total value of the capital
• Re = cost of equity
• Rd = pre-tax cost of debt
• Tc = corporate tax rate

E/V and D/V are the shares of financing from equity and debt, and they must sum to 1.

If the company has preferred stock, it becomes a third term. Preferred dividends are generally not tax-deductible, so there is no tax adjustment:

WACC = (E/V × Re) + (P/V × Rp) + (D/V × Rd × (1 - Tc)), with V = E + P + D

where P is the market value of preferred stock and Rp its cost, commonly estimated as the annual preferred dividend divided by the preferred share price.

Why weights use market values

The weights should reflect how investors value each claim today, so analysts use market capitalization for equity rather than book value. Book equity reflects historical paid-in capital and retained earnings, and for a profitable company with a long history it can be far below what the shares are worth. Book weights would then overstate the role of debt and understate WACC.

For debt, market value is the trading price of the company’s bonds. When bonds are not traded, or borrowing is mostly bank loans, book value of debt is a common stand-in, since loan values sit closer to their face amount than equity does. Some analysts use a target capital structure instead, reasoning that the discount rate should reflect how the company intends to finance itself over the forecast period. This is often preferred for long-horizon valuations and acquisitions where the debt level is expected to change. Whichever structure is used, the cost of equity and cost of debt should be estimated at that same leverage.

Estimating the inputs

Cost of equity

Equity has no stated price: a bond carries a coupon, a share only an expectation. The cost of equity therefore has to be inferred as the return shareholders require given the risk of owning the stock. If the company fails to deliver it over time, shareholders can sell, pushing the share price down.

The most widely used estimate is the capital asset pricing model:

Re = Rf + β × (Rm - Rf)

• Rf is the risk-free rate, typically a government bond yield. In the US, Treasury yields are the usual benchmark, often with a maturity matched to the valuation horizon.
• β (beta) measures how much the stock’s returns move relative to the market: 1.0 means in line with it, above 1.0 more, below 1.0 less.
• Rm - Rf is the equity risk premium, the extra return investors expect from the stock market over the risk-free asset.

Each piece is an estimate. Beta changes with the time window, return frequency and index used, and the equity risk premium differs depending on whether it is derived from historical returns or forward-looking models. Because CAPM relies on past data to forecast a required return, it cannot precisely predict what investors will demand.

Alternatives exist. The dividend discount (Gordon growth) approach estimates Re as next year’s dividend divided by the share price, plus the expected dividend growth rate. A build-up method, common for small and private companies that have no traded shares, starts from the risk-free rate and adds premiums for equity risk, company size and company-specific factors.

Cost of debt

The cost of debt is more direct, because lenders state what they charge. For a public company with traded bonds, the usual measure is the yield to maturity on its outstanding debt, averaged across issues. The yield is preferred over the coupon rate because the coupon was set at issuance, while the yield reflects what the market demands now.

For companies without traded debt, a common approach adds the credit spread for the company’s credit rating (from agencies such as Moody’s or S&P Global, or an estimated equivalent) to a risk-free benchmark such as a Treasury bond of similar maturity. Another approach divides interest expense by average total debt, though that reflects historical rather than current borrowing terms.

The tax adjustment

In the US and many other tax systems, businesses can deduct interest expense when computing taxable income. If a company pays $100 of interest and faces a 25% tax rate, its tax bill falls by $25, so the net cost of that interest is $75. That is why the debt term is multiplied by (1 - Tc). The saving is known as the interest tax shield.

Two cautions apply. The shield only has value if the company has taxable income to offset, so a company with losses gets little or no benefit in the current period, and US rules cap the deduction for business interest in certain cases. The tax rate used should be the marginal rate on additional income, which can differ from the reported effective tax rate.

Example of WACC

In this hypothetical example, a company has 50 million shares trading at $12, so its equity market value is $600 million. Its debt has a market value of $400 million. Total capital V is $1 billion.

Step 1: Weights

• E/V = $600M / $1,000M = 0.60
• D/V = $400M / $1,000M = 0.40

Step 2: Cost of equity (CAPM)

Assume a risk-free rate of 4%, a beta of 1.2 and an equity risk premium of 5%.

Re = 4% + 1.2 × 5% = 4% + 6% = 10%

Step 3: After-tax cost of debt

Assume the company’s bonds yield 6% to maturity and its marginal tax rate is 25%.

After-tax Rd = 6% × (1 - 0.25) = 4.5%

Step 4: Combine

• Weighted cost of equity = 0.60 × 10% = 6.0%
• Weighted cost of debt = 0.40 × 4.5% = 1.8%
• WACC = 6.0% + 1.8% = 7.8%

On these assumptions, the company needs to earn about 7.8% a year on its capital.

Sensitivity check. With a beta of 1.0 instead of 1.2, the cost of equity falls to 9%, the weighted cost of equity to 5.4%, and WACC to 7.2%. A 0.2 change in one estimated input moved WACC by 0.6 percentage points. Over many years of discounting, a shift of that size can change a valuation considerably, which is why analysts often show results across a range of discount rates.

How WACC is used

Discount rate in DCF valuation

In a discounted cash flow (DCF) model, WACC is the rate used to discount unlevered free cash flow, the cash a business generates before any payments to lenders or shareholders. Because those cash flows belong to all capital providers, the discount rate must reflect all their required returns. The present value of those cash flows, plus a discounted terminal value, gives the company’s enterprise value. Subtracting net debt then yields the value of the equity.

The matching matters. Cash flows available only to shareholders (free cash flow to equity, after interest and debt repayments) are discounted at the cost of equity, not WACC. Mixing the two, for example discounting equity cash flows at WACC, produces an inconsistent valuation.

Hurdle rate for projects and acquisitions

A company evaluating an investment can discount the project’s expected cash flows at WACC and compute its net present value. A positive NPV means the project is expected to return more than the cost of the capital funding it. Equivalently, a project whose internal rate of return exceeds WACC clears the hurdle. Money for an acquisition expected to return less than the cost of capital could be better used paying down debt or returning it to shareholders.

Measuring value creation

Comparing a company’s return on invested capital with its WACC shows whether it is creating value. A business that earns 12% on capital that costs it 8% adds value with each dollar invested; one that earns 6% on that same 8% capital destroys value even if it reports accounting profits. Measures such as economic value added are built on this spread.

Capital structure and WACC

Capital structure is the mix of debt and equity a company uses to fund itself, and it drives the weights in the formula. Debt is typically cheaper than equity, because lenders have a prior claim on cash flows and assets and interest is tax-deductible, but adding debt does not simply lower WACC.

As leverage rises, a larger share of operating cash flow is committed to interest before anything reaches shareholders, so their required return and beta go up, and lenders charge more as default risk increases. Modigliani and Miller showed in 1958 that, in a world without taxes or bankruptcy costs, these effects offset exactly and capital structure does not change the cost of capital. Taxes give debt an advantage through the interest tax shield; financial distress costs eventually reverse it. WACC therefore tends to fall as moderate debt is added and then rise as leverage becomes excessive.

The debt-to-equity ratio, which compares a company’s liabilities to its shareholder equity, shows where a company sits on this spectrum. A higher ratio is often read as higher financial risk. When estimating beta from comparable firms with different leverage, analysts commonly “unlever” each comparable’s beta to strip out the effect of debt and then “relever” it at the target company’s capital structure.

WACC vs. related measures

WACC vs. cost of equity. The cost of equity is the return required by shareholders alone. WACC blends it with the cheaper after-tax cost of debt, so for a company with any debt, WACC is normally below the cost of equity. The cost of equity is the right rate for valuing equity cash flows; WACC is the right rate for valuing the whole firm.

WACC vs. required rate of return (RRR). RRR is the minimum return an investor will accept on a given investment, such as a single stock, and is often estimated with CAPM. WACC is a company-level figure that combines the required returns of all capital providers. It is one way to estimate RRR for an investment in the whole business, with the advantage of reflecting the company’s mix of debt and equity.

WACC vs. return on equity. Return on equity is an accounting outcome: net income relative to shareholder equity. WACC is a market-based cost. One measures what the company earned; the other measures what its capital providers require.

WACC vs. a project-specific discount rate. WACC describes the risk of the company’s existing mix of businesses. A diversified company considering a venture far riskier than its core operations should use a higher rate for that venture, often derived from WACC estimates for companies that specialize in that line of business. Applying the corporate WACC across the board makes risky projects look better than they are and safe projects look worse.

What is a good WACC?

There is no single good figure. WACC depends on prevailing interest rates, the industry, the company’s maturity and its capital structure. A stable utility with predictable revenue and substantial debt capacity will usually have a lower WACC than a young technology company with volatile earnings funded mostly by equity. The useful comparisons are against industry peers, the company’s own history and its return on invested capital. What matters for value creation is that returns on new investments exceed WACC, regardless of its absolute level.

Interest rate levels shift every company’s WACC at once. When risk-free yields rise, both the cost of equity (through Rf in CAPM) and the cost of debt tend to rise, which lowers the present value of future cash flows across the market.

Limitations of WACC

• Estimated inputs. The cost of equity, beta and the equity risk premium are not observable, so published WACC figures for the same company can disagree.
• Complex balance sheets. Several debt classes, convertible securities, leases, preferred stock or debt in multiple currencies require more components and more judgment about each one.
• Changing conditions. Interest rates, tax rates, credit spreads and share prices move, so a WACC can be stale within months. Long DCF models typically still assume a constant WACC even though the capital structure may change over the forecast.
• Circularity. Market-value weights depend on equity value, which is what a DCF tries to estimate using WACC. Analysts often break the loop with a target capital structure or by iterating.
• Sensitivity. Because the discount rate compounds over many periods and the terminal value often accounts for a large share of a DCF result, small changes in WACC can produce large changes in valuation.

FAQs

The Bottom Line

WACC matters to analysts valuing a whole company and to managers deciding which projects and acquisitions to fund. A project or business creates value only when its returns exceed WACC, so the absolute level of WACC matters less than that spread. Because the inputs are estimates and small changes move valuations sharply, results are best shown across a range of discount rates, with higher rates for ventures riskier than the core business.