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40-Year Mortgage Calculator

While not super common, there are a number of lenders out there that offer 40-year mortgages.

So I figured it’d be useful to create a 40-year mortgage calculator that shows you what the extended loan term does to your monthly payment and total interest expense.

The main draw of a 40-year loan is to reduce the monthly payment, but it doesn’t often result in a massive difference in payment.

For example, a $400,000 loan at a rate of 6.75% is only about $50 cheaper per month versus a 30-year fixed (at a lower 6.25%).

But those looking for increased cash flow might still be interested, especially at higher loan amounts. Or if the mortgage rates are roughly the same.

40-Year Loan Calculator

Compare a 40-year mortgage against a 30-year loan side by side. See how the extended term affects your monthly payment, total interest paid, equity buildup, and full amortization schedule — so you know exactly what the lower payment costs you over time.

Loan Details

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$
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40-year rates are typically 0.25–0.50% higher than 30-year rates.
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Used for the side-by-side comparison.
Remaining years after I/O period ends.
A 40-year I/O loan has an interest-only period followed by a fully amortizing period.

PITIA & Monthly Liabilities

Add taxes, insurance, and fees for a complete PITIA payment and accurate DTI on both loan scenarios.

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of home price per year
%
$
of home price per year
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PMI/MIP — leave at 0 if not applicable.
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Car loans, student loans, credit card minimums, etc.
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$
Optional — used to calculate DTI for both scenarios.
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Updates as you fill in the fields above.

PITIA Payment Breakdown

40-Year vs. 30-Year Comparison

Remaining Loan Balance Over Time

Amortization Schedule

Disclaimer: This calculator is for informational and educational purposes only and does not constitute financial, legal, or tax advice. 40-year mortgages are considered non-QM loans and are not available through all lenders. Rates, terms, and availability vary. Property tax and insurance figures are estimates. Results do not guarantee loan approval or reflect actual lender offerings. Consult a licensed mortgage professional before making any financial decisions.

The 40-year mortgage calculator above allows you to compare a 40-year mortgage versus a 30-year mortgage side by side.

Once you enter your purchase price, down payment, and interest rate for each type of loan, you’ll be able to quickly calculate and compare the loans.

If it’s a refinance, just enter the loan amount and put zero for the down payment.

You can also enter property taxes, homeowners insurance, mortgage insurance and HOA dues if applicable, and even calculate your DTI ratio using gross monthly income and other liabilities.

[Searching for a home loan? See your options with dozens of lenders fast.]

Those are optional fields so you can enter zero if you’d like to focus solely on the principal and interest payments.

But if interested, you’ll be able to see your DTI ratio on a 40-year loan and a 30-year loan, assuming the lender qualifies you at the 40-year term.

That could be enough to qualify, though chances are it’s more about simply boosting cash flow.

There’s also a full 40-year vs. 30-year comparison with key details including the amount of equity built after five and 10 years, along with the gap between the two loan types.

Lastly, there’s an amortization schedule that shows both the 40-year and 30-year loan balances month-to-month and year-over-year.

So you can see how your loan is repaid over time depending on the loan type.

The main tradeoff between the two loan types is a lower payment on the 40-year mortgage in exchange for a higher interest expense.

In other words, you save on monthly payments but pay for it with more interest over time.

Of course, most homeowners probably won’t keep the 40-year loan to term, whether it’s due to a home sale or a mortgage refinance.

Colin Robertson
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