Cost of Capital Calculator

The cost of capital calculator produces the exact simplified result shown in the form: cost of debt plus cost of equity. It then compares that total with an expected project return. That is a deliberately simple hurdle-rate check, not a full weighted average cost of capital model. In corporate finance, cost of capital usually refers to the blended return required by lenders and shareholders, with each source weighted by how much capital it provides. This tool does not request debt weight, equity weight, or tax rate, so the calculation below uses that simplified method.

Use the result when you want a fast classroom-style comparison, when you are checking whether a proposed return is comfortably above the two financing costs entered, or when you need a conservative preliminary hurdle before building a proper WACC calculator case. For a capital structure model, pair this page with the cost of equity calculator, the after-tax cost of debt calculator, and the discount rate calculator.

What the result means

Capital has an opportunity cost. Lenders expect interest or yield for supplying debt. Equity investors expect a return for taking residual business risk. The calculator asks for those two rates in percentage points and adds them without weighting. If you enter 5 for debt and 8 for equity, the displayed cost of capital is 13%. The optional spread is the expected project return minus that 13% hurdle. A positive spread appears when the project return clears the hurdle; a negative spread appears when it does not.

The distinction matters because a real company rarely finances itself with 100% debt and 100% equity at the same time. A WACC model might weight 5% after-tax debt at 30% of capital and 8% equity at 70% of capital, producing a blended rate near 7.1%, not 13%. This calculator intentionally does not perform that weighted blend. Treat its output as a simplified screen, a sensitivity anchor, or a conservative placeholder until you have the capital mix needed for WACC.

Formula used by this calculator

The calculator uses the two entered percentages directly:

$\text{cost of capital} = \text{cost of debt} + \text{cost of equity}$

It also calculates the project-return spread:

$\text{return spread} = \text{expected project return} - \text{cost of capital}$

These formulas use the simplified method described above. They do not apply debt weights, equity weights, market-value capital structure, or a debt tax shield. If your analysis needs those details, use this page only as a simple comparison and move to a WACC workflow before making an investment decision.

Example: calculating a simplified cost of capital

Suppose a company enters a 5.00% cost of debt, an 8.00% cost of equity, and an expected project return of 15.00%. The calculator adds the first two inputs:

$\text{cost of capital} = 5.00\% + 8.00\% = 13.00\%$

Then it subtracts that hurdle from the project return:

$\text{return spread} = 15.00\% - 13.00\% = 2.00\%$

The primary result is 13.00%. The supporting rows show cost of debt at 5.00%, cost of equity at 8.00%, and expected return spread at +2.00%. If the expected project return were 11.00% with the same debt and equity inputs, the cost of capital would still be 13.00%, but the spread would be -2.00%. That negative spread does not automatically reject the project, but it says the expected return is below the simplified hurdle you entered.

Role in valuation and capital budgeting

Cost of capital is the rate that connects financing risk with operating decisions. In capital budgeting, it acts as a hurdle: projects should earn more than the capital they consume. In discounted cash flow valuation, it becomes the discount rate when cash flows are measured before financing and belong to all capital providers. In performance analysis, it is the benchmark for ROIC: a company that earns a return on invested capital above its cost of capital can create value as it reinvests, while a company below the hurdle may grow revenue without increasing intrinsic value.

This calculator is useful at the earliest stage because it keeps the inputs visible. You can ask, “What if debt costs rise by one point?” or “What if equity investors require a double-digit return?” and immediately see how the hurdle and spread move. That speed is valuable for brainstorming, but the simplicity is not enough for board-level capital allocation. Once a decision matters, document your capital structure, choose market values where appropriate, estimate after-tax debt cost, and justify the equity return with CAPM, dividend growth, or another transparent method.

Common caveats

• This page adds debt cost and equity cost; it does not calculate weighted average cost of capital.
• The debt input is not automatically tax-adjusted. If you want after-tax debt cost, calculate it first and enter that rate intentionally.
• The equity input is an estimate, not a promised shareholder return.
• The expected return spread is only as reliable as the expected project return.
• Nominal rates should be compared with nominal returns; real rates should be compared with real returns.
• A single hurdle rate can hide project-specific risk, especially for projects outside the company’s core business.

Sources

• CFI, WACC Formula — weighted average cost of capital structure and component-cost context.
• NYU Stern, Damodaran, Cost of Capital by Industry — market-based cost of capital reference data.
• Wall Street Prep, WACC — cost of capital and WACC training reference.