How Much Interest a $350,000 Mortgage Costs Over 30 Years: A Closer Look

The choice between a 30-year and a 15-year mortgage is one of the most consequential decisions a homebuyer makes—especially when considering the total cost of ownership over time. For a $350,000 mortgage, the trade-offs between monthly affordability and lifetime interest expense become starkly visible. The table below shows how different interest rate ranges affect monthly payments and total interest paid over the life of each loan term.

$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

The data reveals a clear pattern: at lower APRs, the difference in monthly payments between a 15-year and 30-year mortgage is modest, but the lifetime interest burden is significantly higher on the 30-year option. For example, at an APR of 4%, the 30-year loan results in nearly $100,000 more in total interest paid than the 15-year loan—despite the latter’s higher monthly payment. This gap widens as rates rise, but the cost of borrowing remains asymmetric. At the lower end of the APR range—say, 3% to 4%—the 15-year mortgage offers a more efficient use of capital. The higher monthly payment is offset by a dramatic reduction in total interest. Over 30 years, the 30-year loan at 4% could cost over $130,000 in interest, while the 15-year version would cost just under $80,000. This represents a savings of nearly $50,000 in interest, which is equivalent to over 15 years of a typical monthly grocery budget. However, this efficiency comes with a cost. The 15-year mortgage demands a larger monthly payment—often 30% to 50% more—especially at higher APRs. At 6%, the 30-year loan’s monthly payment increases by about $1,000, while the 15-year payment jumps by over $1,300. This makes the 15-year option less accessible for many borrowers with tight budgets, even if the long-term interest savings are substantial. In practical terms, the 30-year mortgage provides greater flexibility for early retirement, job transitions, or financial uncertainty. It spreads the burden over a longer period, making payments more manageable in the short term. Yet, the lifetime interest cost is a hidden tax on homeownership—especially when rates remain stable or rise. For someone with a stable income and long-term stability, the 15-year option may offer better financial health, even if it feels more demanding. Conversely, if a borrower expects to sell the home within 10 to 15 years—perhaps due to a career move or relocation—the 30-year loan may be more practical. The lower monthly payment allows for greater cash flow, even if it means paying more in interest over time. The key insight from the data is not about which loan is "better" in absolute terms, but about alignment with financial goals. A 30-year mortgage may feel more accessible today, but it comes with a lifetime cost that can be difficult to reverse. A 15-year loan may feel aggressive, but it locks in a lower total interest expense—over 30 years, that’s a difference of $40,000 to $70,000, depending on the rate. How we calculated this: We used standard mortgage amortization formulas to compute monthly payments and total interest paid over 30 and 15 years. The monthly payment formula is: **P = [r × PV] / [1 - (1 + r)^(-n)]** Where P is the monthly payment, r is the monthly interest rate (APR/12), PV is the loan amount ($350,000), and n is the number of months (360 for 30 years, 180 for 15 years). Total interest is the sum of all monthly payments minus the principal. All calculations assume no prepayments or refinancing. The APR range used is based on current market data from U.S. mortgage lenders, spanning 3% to 7%.