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Cost of Capital Calculator

Last updated: March 4, 2026
Reviewed by: LumoCalculator Team

Estimate company cost of capital using the WACC structure: weighted cost of equity plus weighted after-tax cost of debt. Enter CAPM assumptions (risk-free rate, beta, market risk premium), debt cost, tax rate, and financing mix to build practical hurdle-rate and discount-rate scenarios.

Cost of Capital Inputs

Set financing mix and CAPM assumptions to estimate WACC for planning discount-rate scenarios.

Quick Presets

Capital Structure (Market Value)

Cost of Equity (CAPM)

Debt and Tax Assumptions

Cost of Capital Results

Weighted average cost of capital (WACC)

Elevated Capital Cost

9.34%

Total capital evaluated: $10,000,000.00

Cost of equity (Ke)

10.55%

After-tax debt cost

4.50%

Equity weight

80.00%

Debt weight

20.00%

Formula: WACC = (E / (E + D)) x Ke + (D / (E + D)) x Kd x (1 - T)

Calculation line: (80.00% x 10.55%) + (20.00% x 4.50%) = 9.34%

Contribution bridge: Equity 8.44% + Debt 0.90%

Assessment

Estimated cost of capital is 9.34% with equity contributing 8.44% and debt contributing 0.90%.

Use this as a baseline hurdle rate, then stress-test equity risk premium, leverage mix, and debt spread assumptions.

Detailed Breakdown

Equity market value

$8,000,000.00

Debt market value

$2,000,000.00

Tax rate assumption

25.00%

Reference Inputs and Interpretation

Reference inputHow it is usedWhy it matters
Market-value capital structureEquity and debt market values set We and Wd weights in the WACC equation.Using stale book weights can misstate current financing economics and hurdle rates.
CAPM cost of equityRisk-free rate, beta, and market risk premium are combined into Ke.Ke is often the largest WACC driver in equity-heavy structures.
Tax shield treatmentDebt cost is multiplied by (1 - tax rate) before weighting.Ignoring tax shield usually overstates debt contribution and total WACC.
Contribution bridgeOutputs separate equity and debt contributions to final WACC.Bridge view helps identify which assumption to stress-test first.

Step-by-step method

Step 1: Capital weights

We = $8,000,000.00 / $10,000,000.00, Wd = $2,000,000.00 / $10,000,000.00

= We 80.00%, Wd 20.00%

Step 2: Cost of equity (CAPM)

4.50% + 1.1 x 5.50%

= 10.55%

Step 3: After-tax cost of debt

6.00% x (1 - 25.00%)

= 4.50%

Step 4: WACC assembly

(80.00% x 10.55%) + (20.00% x 4.50%)

= 9.34%

Sensitivity Snapshot

ScenarioKeAfter-tax KdWACCDelta
Base Case10.55%4.50%9.34%0.00%
Higher Equity Risk11.65%4.50%10.22%+0.88%
Wider Credit Spread10.55%5.25%9.49%+0.15%
Lower Tax Shield10.55%4.80%9.40%+0.06%

Related Calculators

Editorial & Review Information

Reviewed on: 2026-03-04

Published on: 2025-12-05

Author: LumoCalculator Editorial Team

What we checked: We re-checked CAPM and WACC formula mapping, contribution-bridge arithmetic, scenario sensitivity behavior, and source accessibility for core assumption references.

Purpose and scope: This page supports educational discount-rate planning and capital-budgeting comparisons. It does not provide security recommendations, valuation certification, or financing approval advice.

How to use this review: Start with a base case, then stress-test equity risk, debt spread, and tax assumptions to see which input materially changes hurdle rates before using outputs in decision memos.

Formula and Standards Basis

Core equation used by this calculator

WACC = (E / (E + D)) x Ke + (D / (E + D)) x Kd x (1 - T)

Cost of equity uses CAPM: Ke = Rf + beta x (Rm - Rf). This keeps the equity-return assumption transparent and auditable.

ComponentFormulaWhy it matters
Cost of equity (CAPM)Ke = Rf + beta x (Rm - Rf)Required equity return from risk-free rate, systematic risk, and market premium assumptions.
After-tax debt costKd(after tax) = Kd x (1 - T)Debt cost adjusted for tax-shield effect when interest is deductible.
Capital weightsWe = E/(E + D), Wd = D/(E + D)Market-value financing proportions used to scale cost contributions.
WACC assemblyWACC = (We x Ke) + (Wd x Kd x (1 - T))Weighted hurdle rate used as a baseline discount-rate assumption.

Financial Disclaimer

Cost-of-capital estimates are assumption-sensitive. Real financing outcomes can differ due to liquidity shifts, spread repricing, changing leverage policy, tax-rule updates, and market-regime changes. Use results as planning references, not as standalone investment decisions.

Use Scenarios

DCF discount-rate baseline

Build a baseline hurdle rate for valuation work, then compare base and stress outputs before locking discount assumptions.

Capital budgeting threshold

Convert financing mix and cost assumptions into an approval threshold for project IRR and NPV screening.

WACC consistency cross-check

If you already model direct component costs, cross-check scenario logic with the WACC Calculator to verify weight and tax-shield sensitivity consistency.

Formula Explanation

Step 1: Set market-value capital weights

Input market-value equity and debt so weights reflect current financing economics rather than accounting-period book values.

Step 2: Build cost of equity from CAPM

Use risk-free rate, beta, and market risk premium assumptions to calculate Ke. If your team is adjusting premium assumptions, align them with your Risk Premium Calculator workflow.

Step 3: Convert debt cost to after-tax basis

Apply the tax shield factor (1 - tax rate) to pre-tax debt cost to estimate effective debt burden inside WACC.

Step 4: Assemble weighted contributions

Multiply each component by its financing weight and sum to final WACC. Review contribution bridge to identify dominant assumption drivers.

Example Cases

Case 1: Equity-heavy technology profile

Inputs

  • Equity: $90,000,000
  • Debt: $10,000,000
  • Rf: 4.40%, beta: 1.20, MRP: 5.60%
  • Pre-tax debt cost: 5.10%, tax: 21.00%

Computed Results

  • Cost of equity (Ke): 11.12%
  • After-tax debt cost: 4.03%
  • Equity/Debt weights: 90.00% / 10.00%
  • WACC: 10.41%

Interpretation

Equity assumptions dominate hurdle rate movement because financing mix is heavily equity-weighted.

Decision Hint

Prioritize beta and market-premium sensitivity testing before finalizing valuation bands.

Case 2: Utility-style balanced profile

Inputs

  • Equity: $18,000,000
  • Debt: $22,000,000
  • Rf: 4.10%, beta: 0.62, MRP: 5.20%
  • Pre-tax debt cost: 4.60%, tax: 25.00%

Computed Results

  • Cost of equity (Ke): 7.32%
  • After-tax debt cost: 3.45%
  • Equity/Debt weights: 45.00% / 55.00%
  • WACC: 5.19%

Interpretation

Moderate beta and meaningful tax-shielded debt weight keep capital cost comparatively low.

Decision Hint

Validate refinancing risk assumptions because debt share is still structurally significant.

Case 3: Leveraged private transaction

Inputs

  • Equity: $2,500,000
  • Debt: $3,500,000
  • Rf: 4.80%, beta: 1.65, MRP: 6.00%
  • Pre-tax debt cost: 8.30%, tax: 26.00%

Computed Results

  • Cost of equity (Ke): 14.70%
  • After-tax debt cost: 6.14%
  • Equity/Debt weights: 41.67% / 58.33%
  • WACC: 9.71%

Interpretation

Tax shield helps but high equity and debt return requirements keep hurdle rates elevated.

Decision Hint

Pair this output with downside covenant and spread-shock tests before transaction approval.

Industry Beta Context

Utilities

Reference beta: 0.55

Usually lower beta due to regulated cash-flow stability.

Consumer Staples

Reference beta: 0.72

Defensive demand profile often reduces market sensitivity.

Industrials

Reference beta: 1.00

Often near-market risk, depending on cycle exposure.

Financial Services

Reference beta: 1.15

Credit cycle and leverage dynamics can raise beta.

Technology

Reference beta: 1.30

Growth duration and sentiment sensitivity can increase volatility.

Small-Cap Growth

Reference beta: 1.55

Higher operating and financing uncertainty often lifts beta.

Boundary Conditions

Inputs assume a static capital structure per scenario; dynamic re-leveraging over time is not modeled.
CAPM relies on estimated beta and premium assumptions, which can shift materially across market regimes.
Market-value and spread inputs must be refreshed regularly; stale data can misstate hurdle rates.
Project-level risk may differ from company-level risk, so project hurdle rates may need additional adjustment.
The model does not include country-risk add-ons, currency mismatch, or bespoke financing covenants.
Output is rounded for readability; use unrounded internal assumptions for final committee materials.

Sources & References

Frequently Asked Questions

What is the difference between cost of capital and WACC?
Cost of capital is the broad required return concept across financing sources. WACC is the weighted expression of that concept for a specific equity-debt mix and tax assumption. In practice, WACC is often the applied discount-rate baseline for firm-level valuation.
Why does tax rate affect cost of capital in this model?
Debt interest can create a tax shield in many jurisdictions, so after-tax debt cost is lower than pre-tax debt cost. This reduces debt contribution inside WACC when debt weight is meaningful.
How should I choose beta for CAPM assumptions?
Start with a stable industry or peer-set beta range, then adjust for company-specific leverage, cyclicality, and business model risk. Refresh beta assumptions when structure or market regime shifts materially.
Can I use one cost-of-capital number for every project?
Use company-level WACC as a baseline only for projects with similar risk to the core business. Higher-risk or lower-risk projects usually need adjusted hurdle rates rather than a single blanket number.
How often should I refresh assumptions?
Refresh when risk-free rates, credit spreads, equity risk premium assumptions, or target leverage change. For active planning and valuation workflows, quarterly refreshes are common.
Does this calculator provide investment advice?
No. This tool is for educational planning and scenario framing. It does not replace due diligence, underwriting analysis, legal or tax advice, or personalized investment guidance.