Mortgage Tax Savings Calculator
If you itemize, mortgage interest is deductible. Estimate the first-year tax savings and your effective after-tax interest rate.
A worked example
Running this tool on current national benchmarks (Federal Reserve / Freddie Mac via FRED (St. Louis Fed)) — swap in your own numbers to see how the result moves.
- Loan amount
- $300,000
- Interest rate
- 6.50%
- Loan term (years)
- 30
- Marginal tax rate
- 24%
your effective rate drops to 4.94%
- First-year interest$19,401
- Tax savings$4,656
- After-tax interest rate4.94%
How the first-year tax savings changes with loan amount
Holding the other inputs at the example above, here is how the result moves as loan amount changes.
| Loan amount | First-year tax savings | First-year interest |
|---|---|---|
| $150,000 | $2,328 | $9,701 |
| $300,000 | $4,656 | $19,401 |
| $500,000 | $7,761 | $32,335 |
| $750,000 | $11,641 | $48,503 |
The math behind it
The calculator amortizes your loan at the rate and term, then sums the interest paid in the first twelve months. Multiplying that first-year interest by your marginal tax rate estimates your tax savings from the mortgage-interest deduction. It also computes your effective after-tax rate — your interest rate times one minus the tax rate — and projects the shrinking deduction year by year as the interest portion of your payment falls.
Assumptions & limits
- The savings assume you itemize deductions. If your standard deduction is larger, the mortgage interest yields no extra benefit.
- It applies your marginal tax rate to mortgage interest only; it does not model deduction phase-outs or the loan-size limit on deductible interest.
- First-year interest is highest and the deduction shrinks each year as you pay down principal, which the yearly schedule reflects.
- State tax effects and the alternative minimum tax are not modeled.
- A single fixed interest rate is assumed for the term.
When the mortgage-interest deduction helps
The deduction only adds value beyond the standard deduction you would take anyway.
| Situation | Effect |
|---|---|
| Itemized deductions exceed the standard deduction | Mortgage interest reduces taxable income |
| Standard deduction is larger | No added benefit from the mortgage interest |
| After-tax rate | Rate times (1 minus marginal tax rate) |
Source: Freddie Mac PMMS via FRED. Annual averages; latest weekly reading shown.
Common questions
Do I get this tax savings if I take the standard deduction?
No. The mortgage-interest deduction only helps if your total itemized deductions exceed the standard deduction. Since the standard deduction was raised, many homeowners no longer itemize and see no benefit. Compare your itemized total against the standard deduction before counting on these savings.
What is an after-tax interest rate?
It is what your mortgage effectively costs once the interest deduction is factored in — your rate times one minus your marginal tax rate. A 6.5% loan for someone in the 24% bracket who itemizes costs roughly 4.9% after tax. It only applies to the extent the deduction actually benefits you.
Why does the tax savings shrink each year?
Early payments are mostly interest, so the deductible amount is largest at the start. As principal is paid down, less of each payment is interest, and the deduction — and the savings — decline. The yearly schedule in the results shows this decline.