Finance

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After-Tax Cost of Debt Calculator.

Estimate after-tax cost of debt from a pre-tax rate and marginal tax assumption.

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Results update as you type.

After-tax cost of debt: 6 %

After-tax cost of debt

6.000%

FAQs

Is the tax shield guaranteed?

No. The result is a simplified estimate and does not model tax eligibility, limits, fees, or jurisdiction-specific rules.

Cite this calculator

Canonical URL: https://mathify.one/de/finance/after-tax-cost-of-debt

Cite as: Mathify. (2026). Rechner: After-Tax Cost of Debt. https://mathify.one/de/finance/after-tax-cost-of-debt

Use Cases

Corporate Financial Analysis

Determine the true cost of debt for capital budgeting, weighted average cost of capital (WACC) calculations, and investment decisions.

Example: A company with a 6% loan and 25% tax rate has an after-tax cost of 4.5%.

Comparing Financing Options

Evaluate different debt instruments or loan terms by comparing their after-tax costs, helping choose the most cost-effective financing.

Example: Compare a 5% bond vs. a 6% loan, considering tax rates.

Frequently Asked Questions

What is the after-tax cost of debt?
It is the effective interest rate a company pays on its debt after accounting for the tax deductibility of interest. It is calculated as pre-tax cost of debt multiplied by (1 - marginal tax rate).
Why is the after-tax cost of debt lower than the pre-tax cost?
Because interest payments are tax-deductible, they reduce taxable income. The tax savings lower the net cost of borrowing, making the after-tax cost lower than the stated interest rate.
How do I use this calculator?
Enter your pre-tax cost of debt (interest rate) and your marginal tax rate. The calculator will apply the formula to estimate your after-tax cost of debt, showing the impact of the tax shield.

Tips & Common Mistakes

Tips

  • Use your marginal tax rate, not your average tax rate, for the most accurate estimate.
  • Remember that the tax shield only applies if your business is profitable and pays taxes.
  • For personal debt, interest may not be tax-deductible; this calculator is primarily for business debt.
  • Re-calculate after-tax cost whenever your tax rate or interest rate changes.

Common Mistakes to Avoid

  • Using the average tax rate instead of the marginal tax rate, which can skew results.
  • Forgetting that the tax shield is only valuable if you have taxable income to offset.
  • Confusing the pre-tax cost with the after-tax cost when comparing loan options.

Last updated: August 13, 2026