The Cost of a $400,000 Mortgage Across Different Rates

The choice between a 30-year and a 15-year mortgage is one of the most impactful financial decisions a homebuyer makes—especially when the loan amount is $400,000. While both options provide a path to homeownership, the trade-offs in monthly payments, total interest paid, and long-term financial health vary significantly depending on current interest rates. The table below shows how different APR ranges affect the monthly payment and lifetime interest cost for a $400,000 mortgage across the two loan terms.

$400,000 mortgage — monthly payment and lifetime interest, 30-year vs 15-year, by rate

Rate	30-yr Payment	30-yr Interest	15-yr Payment	15-yr Interest
6.0%	$2,398	$463,353	$3,375	$207,577
6.5%	$2,528	$510,178	$3,484	$227,197
7.0%	$2,661	$558,036	$3,595	$247,156
7.5%	$2,797	$606,869	$3,708	$267,449

A 30-year mortgage offers lower monthly payments, making it more accessible for buyers with tighter budgets or those who plan to stay in a home for decades. However, it comes with a much higher lifetime interest cost—often 3 to 5 times more than a 15-year loan—because interest is paid over a longer period. For example, at a 5% APR, a 30-year loan will result in nearly $300,000 in total interest, while a 15-year loan at the same rate will pay about $120,000. This difference grows wider at higher APRs, where the cumulative interest burden on a 30-year loan becomes substantially greater. In contrast, a 15-year mortgage is designed for borrowers who want to pay off their loan faster and minimize total interest. It typically requires higher monthly payments—often 1.5 to 2 times more than a 30-year loan—due to the shorter repayment period. However, the monthly burden is offset by significantly lower lifetime interest. At a 4% APR, the 15-year loan pays roughly $70,00 as total interest, compared to over $170,000 for the 30-year version. This makes the 15-year option especially compelling for those with stable incomes and a clear plan to stay in their home for at least 15 years. The decision between the two terms also depends on the current APR environment. In a low-rate environment (e.g., 3% to 4%), the 15-year mortgage may offer a more efficient path to wealth accumulation because of the lower interest burden. At higher APRs (e.g., 6% to 7%), the advantage of a 15-year loan grows even more pronounced, as the difference in total interest can exceed $100,000. This means that for every 1% increase in APR, the 30-year loan pays nearly $20,000 more in interest than the 15-year loan over its life. It’s important to note that a 30-year mortgage may seem more flexible, but it doesn’t offer greater equity growth—it simply spreads the cost of borrowing over more years. A 15-year loan, while demanding in the short term, builds equity faster and reduces the total cost of ownership over time. This makes it a better fit for borrowers who prioritize long-term financial efficiency, such as those with established careers or long-term homeownership goals. For borrowers who plan to refinance or sell within 10 years, the 30-year option may still make sense due to lower monthly payments. But for those who intend to stay in a home for 20 years or more, the 15-year mortgage offers a clearer path to financial stability and reduced interest exposure. How we calculated this: We used standard mortgage formulas to compute monthly payments and total interest paid over the loan term. The monthly payment is derived from the formula: M = P × [r(1+r)^n] / [(1+r)^n – 1] where M is the monthly payment, P is the principal ($400,000), r is the monthly interest rate (APR ÷ 12), and n is the number of payments (30 or 15 years × 12). Total interest is then calculated by subtracting the principal from the total payments over the life of the loan. All figures are based on current APR ranges and do not include taxes, insurance, or fees.