Tax-Equivalent Yield Calculator

Tax-free municipal bonds occupy a unique place in many investors’ portfolios. The interest they pay is often exempt from federal income tax, and in some cases from state and local taxes as well. This tax advantage can make a municipal bond with a seemingly modest yield more attractive than a taxable bond with a higher headline yield. The challenge is that you cannot simply compare the two yields directly—you need to adjust for taxes.

The tax-equivalent yield (TEY) solves this problem by answering a simple question: “What yield would a taxable bond need to offer to match the after-tax return of a tax-free municipal bond?” The Tax-Equivalent Yield Calculator implements this concept using a straightforward formula and adds practical comparison metrics so you can see the impact in dollar terms.

The core formula for tax-equivalent yield is:

Tax-equivalent yield (TEY):
TEY = taxFreeYield / (1 − taxRate)

Here, taxFreeYield is the annual yield of the municipal bond expressed as a percentage, and taxRate is your marginal tax rate on interest income, also expressed as a decimal (for example, 0.24 for 24%). The denominator (1 − taxRate) represents the portion of taxable interest you keep after paying taxes. Dividing the tax-free yield by this factor tells you what taxable yield would be required to deliver the same after-tax return.

The calculator lets you model both federal and state taxes. If your municipal bond is exempt from state tax, you may choose to use only your federal rate in the calculation. If you want to reflect both federal and state taxes on taxable bond interest, you can combine them into a single marginal rate. The tool computes an effective marginal tax rate as:

Effective marginal tax rate:
effectiveRate = combinedRate
or, if you prefer to derive it from separate inputs:
effectiveRate ≈ federalRate + stateRate (simplified, ignoring interactions)

In practice, the calculator uses the combinedRate field if you provide it; otherwise, it approximates the effective rate by adding federal and state rates. This is a simplification, but it is useful for planning and comparison.

The tool also computes the implied tax-free yield from a taxable bond. This is the inverse of the TEY formula:

Implied tax-free yield from taxable bond:
impliedTaxFreeYield = taxableYield × (1 − taxRate)

This tells you what tax-free yield would deliver the same after-tax return as a given taxable yield. If the municipal bond’s actual tax-free yield is higher than this implied value, it may be more attractive on an after-tax basis, assuming similar risk and credit quality.

To make the comparison more tangible, the calculator uses your investment amount to compute annual income from each option. For the municipal bond:

Annual tax-free income (muni):
annualMuniIncome = investmentAmount × taxFreeYield / 100

For the taxable bond, the calculator first computes the annual interest:

Annual taxable interest:
annualTaxableInterest = investmentAmount × taxableYield / 100

Then it applies the effective tax rate to estimate after-tax income:

Annual after-tax income (taxable bond):
annualTaxableAfterTax = annualTaxableInterest × (1 − taxRate)

The difference between the two annual income figures is:

Difference in annual income:
annualDifference = annualMuniIncome − annualTaxableAfterTax

A positive difference means the municipal bond provides more income after taxes; a negative difference means the taxable bond comes out ahead. By multiplying these annual figures by your holding period in years, you can approximate the cumulative income difference over time, though the calculator focuses on annual metrics for clarity.

Consider a practical example. Suppose you are in a 32% federal bracket and a 5% state bracket, and you treat your municipal bond as exempt from state tax. You might use a combined marginal rate of 32% for the TEY calculation. If your municipal bond yields 3.25%, the tax-equivalent yield is:

TEY = 3.25% / (1 − 0.32) ≈ 3.25% / 0.68 ≈ 4.78%

This means a taxable bond would need to yield about 4.78% to match the after-tax return of the 3.25% tax-free municipal bond. If you are comparing it to a corporate bond yielding 4.10%, the implied tax-free yield of that corporate bond is:

impliedTaxFreeYield = 4.10% × (1 − 0.32) ≈ 4.10% × 0.68 ≈ 2.79%

In this scenario, the municipal bond’s 3.25% tax-free yield is clearly more attractive than the corporate bond’s 2.79% implied tax-free yield, assuming similar risk and credit quality.

If you invest \$50,000, annual tax-free income from the municipal bond is:

annualMuniIncome = 50,000 × 3.25% ≈ 1,625

Annual taxable interest from the corporate bond is:

annualTaxableInterest = 50,000 × 4.10% ≈ 2,050

After taxes at 32%, you keep:

annualTaxableAfterTax = 2,050 × (1 − 0.32) ≈ 2,050 × 0.68 ≈ 1,394

The annual income difference is:

annualDifference ≈ 1,625 − 1,394 ≈ 231

Over a five-year holding period, this difference would accumulate to roughly \$1,155, ignoring reinvestment and price changes. The calculator helps you see these differences quickly and adjust your assumptions to reflect your actual tax situation.

The investor profile, notes, and risk/credit comment fields are there to remind you that yield is only one dimension of the decision. A high-yield taxable bond may carry more credit risk or interest rate sensitivity than a high-quality municipal bond. Tax-equivalent yield is a powerful lens, but it should be combined with a broader view of risk, diversification, and your overall financial plan.

Because tax rules can be complex and subject to change, this calculator is best used as an educational tool and a starting point for analysis. For detailed tax planning, you should review official guidance and consider working with a qualified advisor. You can also pair this tool with others in the MyGenFinance suite—such as the Effective Tax Rate Calculator, After-Tax Income Calculator, and Tax Bracket Change Impact tool—to build a more complete picture of how taxes affect your investment and income decisions.