WACC Calculator (Cost of Capital)

WACC = (E/V × Re) + (D/V × Rd × (1-T)), where E is market value of equity, D is market value of debt, V = E+D, Re is cost of equity, Rd is cost of debt, and T is the corporate tax rate. Cost of equity is typically estimated using the Capital Asset Pricing Model: Re = Rf + β(Rm - Rf), where Rf is the risk-free rate (10-year Treasury yield, approximately 4.5% in 2026), β is the stock's beta (systematic risk relative to the market), and (Rm - Rf) is the equity risk premium (historically 5-7%). Cost of debt is the yield on existing bonds or the interest rate on bank loans — importantly adjusted for the tax deductibility of interest: a 6% interest rate at a 21% tax rate has an after-tax cost of only 4.74%.

WACC varies significantly by industry due to differences in business risk, capital structure, and beta. Utilities typically have the lowest WACC (5-7%) due to stable cash flows, high leverage capacity, and low betas (0.3-0.6). Technology companies range from 8-12% with higher betas (1.0-1.5) and less debt capacity. Biotech and early-stage companies may face WACC of 12-20% reflecting high equity costs and limited debt access. Real estate companies (REITs) benefit from tax-advantaged structures and stable cash flows, with WACC of 6-8%. The overall S&P 500 average WACC is approximately 8-9%. Using an incorrect WACC of even 1-2 percentage points can dramatically alter DCF valuations — on a $10 million annual cash flow valued in perpetuity, the difference between 8% and 10% WACC is $25 million in enterprise value.

The most frequent error is using book value instead of market value weights. A company with $50M book equity and $50M book debt might have $200M market cap, making the true equity weight 80% rather than 50% — significantly affecting the weighted average. Using the coupon rate on old bonds rather than the current yield to maturity overstates or understates the cost of debt. Applying a domestic risk-free rate and equity premium to international operations ignores country risk — emerging market investments require a country risk premium of 2-8% added to WACC. Ignoring the tax shield on debt (using pre-tax Rd instead of Rd × (1-T)) overstates WACC by 1-2 percentage points. Finally, using a single WACC for all divisions of a diversified company is inappropriate — a conglomerate's software division and manufacturing division have very different risk profiles and should use divisional WACCs.

Weighted average cost of capital (WACC) is the blended rate of return a company must earn to satisfy every provider of capital — its shareholders and its lenders — weighted by how much of each it uses.

The formula combines two costs:

• Cost of equity (Re) — the return shareholders demand for holding the stock
• After-tax cost of debt (Rd × (1 − T)) — the interest rate on borrowings, reduced by the tax deduction on interest

Each cost is weighted by its share of total capital (E/V and D/V), then added together.

The U.S. Securities and Exchange Commission (SEC) frames the cost of capital as the return investors require for the risk they accept. Because debt ranks ahead of equity in bankruptcy and interest is tax-deductible, the debt component is usually the cheaper of the two.

To use this WACC calculator, enter your market value of equity and debt, the cost of equity and pre-tax cost of debt, and your corporate tax rate — it returns WACC instantly.

Work through these steps:

• Enter equity as market capitalization (shares × price), not book value
• Enter debt as the market value of outstanding bonds and loans
• Enter cost of equity directly, or tick CAPM to derive it from beta and the risk-free rate
• Enter the pre-tax cost of debt and your marginal tax rate

Worked example: $60M equity, $40M debt, Re 12%, Rd 6%, tax 21%.

Weights are 60% and 40%; after-tax debt = 6% × (1 − 0.21) = 4.74%; WACC = 0.60 × 12% + 0.40 × 4.74% = 9.10%. Any project must clear 9.10% to add value.

The cost of equity is most often estimated with the Capital Asset Pricing Model (CAPM): Re = Rf + β × (Rm − Rf). It translates a stock's systematic risk into a required return.

The three inputs are:

• Risk-free rate (Rf) — typically the yield on a 10-year U.S. Treasury note, published daily by the U.S. Department of the Treasury and the Federal Reserve (release H.15); check the current figure rather than assuming a fixed value
• Beta (β) — how volatile the stock is relative to the broad market
• Equity risk premium (Rm − Rf) — the extra return investors demand over the risk-free rate, historically observed in a mid-single-digit percentage range

FINRA and the SEC both stress that higher risk should command higher expected return — exactly the effect a rising beta produces in CAPM.

The after-tax cost of debt equals the pre-tax interest rate multiplied by (1 − tax rate), because interest expense is tax-deductible. This "tax shield" is why debt is cheaper than its headline rate suggests.

For example, a 6% rate at a 21% tax rate costs only 6% × (1 − 0.21) = 4.74% after tax.

Keep these points in mind:

• Use the current yield to maturity on outstanding bonds, not the old coupon
• Apply the marginal tax rate the Internal Revenue Service (IRS) sets for the current tax year, since the federal corporate rate can change by legislation
• Deductibility of business interest is governed by IRS rules, which may limit the shield for highly leveraged firms

Only the after-tax figure belongs in the WACC formula.

In a discounted cash flow (DCF) valuation, WACC is the discount rate that converts future free cash flows into present value. Enterprise value = Σ FCF_t ÷ (1 + WACC)^t plus a discounted terminal value.

Because the rate sits in the denominator and compounds over time, small WACC changes move valuations a lot:

• A lower WACC raises present value and the price you can justify
• A higher WACC lowers it
• Analysts run a sensitivity table across a WACC range instead of trusting one point estimate

The SEC reminds investors that valuation models rest on assumptions, and the discount rate is among the most influential. Always document the WACC and the inputs behind any DCF so the result can be scrutinized.

WACC is the natural hurdle rate for capital budgeting: a project should proceed only if its expected return exceeds the company's WACC. Earning above WACC creates value; earning below it destroys value.

Apply it two ways:

• Compare a project's internal rate of return (IRR) to WACC — accept when IRR > WACC
• Or discount the project's cash flows at WACC and accept a positive net present value (NPV)
• Add a premium for projects riskier than the firm's typical business

WACC reflects the firm's overall risk profile. As the SEC and FINRA note, riskier ventures warrant a higher required return, so a single company-wide WACC can misprice a project that is unusually risky or unusually safe.

The most common mistakes when using a WACC calculator are entering inconsistent or mismatched inputs — such as mixing book and market values, or nominal and real rates. Each error skews the output even when the formula itself is correct.

Watch for these input traps:

• Entering percentages as decimals (12 vs 0.12), or the reverse
• Using a stale beta that no longer reflects the company's leverage
• Plugging in an effective tax rate when the marginal rate the IRS applies is more appropriate for the shield
• Omitting preferred stock, a third capital source with its own cost and weight
• Mixing a nominal WACC with real (inflation-adjusted) cash flows — the U.S. Bureau of Labor Statistics (BLS) publishes CPI if you need to convert between the two

Re-check every unit before trusting the result.

Changing a company's mix of debt and equity changes its WACC because debt is cheaper than equity but adds financial risk. Up to a point, adding low-cost debt lowers WACC.

How leverage moves the numbers:

• More debt raises the D/V weight on the cheaper after-tax debt, pulling WACC down
• But rising leverage increases bankruptcy risk, lifting both the cost of debt and the beta-driven cost of equity
• Beyond the optimal capital structure, WACC turns back upward

This trade-off traces to Modigliani–Miller theory, which shows the interest tax shield adds value while financial-distress costs eventually offset it. The Federal Reserve monitors aggregate corporate leverage precisely because excessive debt can threaten broader financial stability.