WACC Calculator (Weighted Average Cost of Capital)
WACC, or weighted average cost of capital, is the blended return a company needs to earn on invested capital to compensate shareholders and lenders. This calculator combines cost of equity, equity value, pre-tax cost of debt, debt value, and corporate tax rate into one percentage. The output is commonly used as a hurdle rate for projects and as a discount rate for free cash flow to the firm.
WACC is distinct from the CAPM calculator, which estimates only the cost of equity from beta and market risk premium. It is also different from the NPV calculator, which uses a discount rate to test a project. In valuation work, WACC often feeds the DCF calculator, while the enterprise value calculator shows the market-value side of the same capital-structure conversation. IRR users can compare project return in the IRR calculator with the WACC hurdle rate.
How this calculator works
Enter cost of equity as an annual percentage. This may come from CAPM, a dividend discount model, observed investor return requirements, or an analyst assumption. Enter equity as the market value of common equity when possible. For a public company, that is usually market capitalization.
Enter cost of debt as a pre-tax annual percentage, such as the yield on outstanding debt or the rate the company would pay to borrow today. Enter debt as the market value or best current estimate of interest-bearing debt. The corporate tax rate reduces the cost of debt because interest is often tax deductible. The calculator applies that tax shield directly.
The output shows WACC, equity weight, debt weight, after-tax cost of debt, and total capital. That breakdown matters because the same WACC can come from very different capital structures.
Formula
The calculator uses two capital sources, equity and debt:
The after-tax cost of debt is:
The weights are:
The calculation shows a validation message only when inputs are not valid numbers, equity or debt is negative, total capital is zero or below, or the tax rate falls outside 0% to 100%.
Worked example using the default inputs
Use the default assumptions: cost of equity 15%, equity value 700,000 dollars, cost of debt 8%, debt value 500,000 dollars, and corporate tax rate 20%. Total capital is 1,200,000 dollars.
| Component | Calculation | Result |
|---|---|---|
| Equity weight | 700,000 divided by 1,200,000 | 58.33% |
| Debt weight | 500,000 divided by 1,200,000 | 41.67% |
| After-tax cost of debt | 8% times one minus 20% | 6.40% |
| Equity contribution | 58.33% times 15% | 8.75% |
| Debt contribution | 41.67% times 6.40% | 2.67% |
| WACC | 8.75% plus 2.67% | 11.42% |
The calculator reports a weighted average cost of capital of 11.42%. It also displays total capital of 1,200,000 dollars and confirms the capital mix: 58.33% equity and 41.67% debt. A project with expected returns above 11.42% may create value for this capital structure, while a project below that level may not compensate investors and lenders for their opportunity costs.
How WACC is used
In a DCF valuation, WACC is commonly used to discount free cash flow to the firm because FCFF is available to both debt and equity providers before financing distributions. If the DCF result is higher than market enterprise value, the company may look undervalued under the assumptions. If it is lower, the assumptions may imply overvaluation or insufficient future cash flow.
In capital budgeting, WACC is a hurdle rate. A new factory, software platform, or acquisition should be expected to earn more than the capital it consumes. Using WACC encourages managers to include both explicit borrowing costs and the less visible cost of shareholder capital. Equity is not free simply because it has no interest coupon.
WACC also helps compare financing strategies. More debt can lower WACC when debt is cheaper and tax-deductible, but too much leverage raises financial risk and may increase both debt and equity costs. The calculator does not model changing risk from leverage; it simply weights the inputs you provide.
Limitations and tips
Use market-based inputs when possible. Book equity can be far below market value for companies with valuable intangible assets, and old debt may not reflect current borrowing costs. Match the tax rate to the debt tax shield actually available; companies with losses or limits on interest deductibility may not receive the full benefit immediately.
Do not use one WACC mechanically across unrelated projects. A mature utility project and an early-stage technology acquisition can have very different risk even inside the same company. Adjust the discount rate or build separate scenarios when project risk differs from the firm’s existing asset base.
Finally, keep units consistent. Enter percentages as percentages, not decimals. For example, enter 15 for 15%, not 0.15. Enter equity and debt in the same currency and as of the same valuation date.
Sources
- CFA Institute, Cost of Capital: Advanced Topics — professional curriculum reference for estimating and applying the cost of capital.
- Internal Revenue Service, Questions and answers about the limitation on the deduction for business interest expense — primary U.S. tax authority explaining that interest deductibility can be limited, which is why the tax-shield assumption needs review.