Cost Of Capital Calculator guide
Cost of capital is the return required by providers of debt and equity. WACC combines those required returns using market-value capital weights.
The existing calculator preserves its detailed equity and debt methods; the new module adds a standardized verified WACC engine and crawlable guidance.
How to use the cost of capital calculator
- Enter current amounts: Use current, documented values from the same relevant period.
- Enter assumptions: Use realistic rates, percentages, periods, and costs where applicable.
- Review the full result: Review the primary estimate together with its supporting measures.
- Stress-test risk: Model less favorable timing, value, cost, or rate assumptions.
Formula and variables
The estimate applies the entered values and assumptions to the stated formula.
WACC = equity weight × cost of equity + debt weight × after-tax debt cost- Inputs — Entered values
- The amounts, percentages, or periods supplied to the calculator.
- Result — Calculated output
- The estimate produced by applying the formula to the entered values.
Worked example: cost of capital calculator
A user enters a representative set of values and assumptions.
- Key inputs
- Amounts, percentages, periods, and costs
- Apply the stated formula.
- Include all relevant entered values and constraints.
- Compare the result with an alternative scenario.
Result: Cost of equity, after-tax debt cost, capital weights, and WACC.
Use the estimate as a planning input and verify important decisions with current records or qualified guidance.
Understanding your results
Primary estimate
Cost of equity, after-tax debt cost, capital weights, and WACC.
Risk measures
Use supporting payment, leverage, cost, and cash figures together.
Assumptions
- Entered rates and costs remain constant.
- Payments and cash flows occur on schedule.
Limitations
- Taxes, legal terms, accounting treatment, and transaction-specific costs may differ.
- Future values, timing, and rates are uncertain.
Common mistakes
- Reviewing only the headline result.
- Ignoring relevant costs, timing, or supporting measures.
- Using optimistic timing or value assumptions.
- Treating an estimate as a guaranteed outcome.
Practical use cases
Compare scenarios consistently
Change one assumption at a time or enter each alternative using the same basis.
Plan cash requirements
Estimate funds needed before committing.
Planning and decision guide
Stress-test the assumptions
Use market values where available and match rates to the valuation currency and horizon.
Review the important risks
Beta, market premium, debt yield, and tax benefit are estimates.
Verify the source values
Use a project-specific rate when project risk differs materially from the company.
Frequently asked questions
What is WACC?
The weighted required return of debt and equity capital.
Why use after-tax debt cost?
Interest can create a tax shield where deductible and usable.
Should weights use book or market value?
Market-value weights are generally preferred for valuation.
Is WACC the discount rate for every project?
No. Adjust for material differences in project risk.
Sources and review
- Introduction to investing — U.S. Securities and Exchange Commission. Accessed 2026-07-10.
Reviewed 2026-07-10.