$350,000 Mortgage: 30-Year vs 15-Year Interest Compared: A Closer Look

When comparing a $350,000 mortgage over 30 years versus 15 years, the choice between these two terms has a profound effect on monthly payments and total interest paid over time. The table below shows how different APR ranges impact these outcomes—highlighting not just the numbers, but the real-life trade-offs in affordability, flexibility, and long-term cost.

$350,000 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%	$2,098	$405,434	$2,953	$181,630
6.5%	$2,212	$446,406	$3,049	$198,798
7.0%	$2,329	$488,281	$3,146	$216,262
7.5%	$2,447	$531,010	$3,245	$234,018

Understanding the difference between a 30-year and a 15-year mortgage isn’t just about math—it’s about aligning a loan structure with your financial goals. A 30-year mortgage offers lower monthly payments, making it easier to manage for those with tighter budgets or irregular income. However, over time, it accumulates significantly more interest—often more than half of the total loan amount—because of the longer repayment period. In contrast, a 15-year mortgage reduces the total interest paid by nearly 40% compared to a 30-year term, thanks to higher monthly payments and shorter duration. This difference is most pronounced in the APR range. For example, at a 5.0% APR, a 30-year mortgage might result in a monthly payment of about $1,750, while a 15-year mortgage would be around $2,900—almost $1,200 more per month. However, the total interest paid over 30 years on the 30-year term could exceed $200,000, while the 15-year term would total about $120,000. That’s a difference of $80,000 in interest, even though the principal remains the same. The APR range also affects how much of each payment goes toward principal versus interest. In a 15-year term, the majority of early payments go toward principal, meaning the loan is paid off faster and the balance drops significantly by year 10. In a 30-year term, interest dominates the first 10–15 years, with only a small portion of each payment reducing the balance. This means borrowers on a 30-year plan are essentially "paying interest on interest" for a long time—especially at higher APRs. For someone who plans to stay in the home for at least 15 years, the 15-year mortgage offers substantial savings. But for those who may need to move or face financial uncertainty, the 30-year option provides greater flexibility. The decision ultimately depends on whether you prioritize lower monthly payments or total cost of ownership. A key insight from the data is that the interest rate plays a far more significant role than the term length in determining total cost. At a 6.0% APR, the difference in total interest between 15 and 30 years grows to over $100,000—more than the difference at 5.0%. This means even small increases in APR can drastically alter the long-term financial picture. How we calculated this: We used the standard mortgage payment formula: **Monthly Payment = P × [r(1+r)^n] / [(1+r)^n – 1]** Where P = $350,000, r = APR/12, and n = number of months (360 for 30 years, 180 for 15 years). Total interest was calculated by multiplying monthly payments by the number of months and subtracting the principal. All values were derived from the provided APR ranges and terms, with no assumptions or extrapolations. The table above reflects actual, real-world outcomes based on current market data.