$300,000 Home Loan: Payment and Lifetime Interest by Rate

When choosing between a 15-year and a 30-year mortgage for a $300,000 loan, the decision isn’t just about monthly payments—it’s about how much you’ll pay over time, especially in interest. The table below shows how monthly payments and total lifetime interest vary between a 15-year and a 30-year term, across a range of current interest rates. These numbers reflect real-world scenarios today, where borrowing costs are sensitive to rate fluctuations and term length.

$300,000 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%	$1,799	$347,515	$2,532	$155,683
6.5%	$1,896	$382,633	$2,613	$170,398
7.0%	$1,996	$418,527	$2,696	$185,367
7.5%	$2,098	$455,152	$2,781	$200,587

A 15-year mortgage offers lower total interest over time and faster equity buildup, but it comes with significantly higher monthly payments—often 30% to 50% more than a 30-year loan at the same rate. For example, at a 5% rate, a 15-year loan might require $2,100 per month, while a 30-year loan would be about $1,490. This difference makes the 15-year option more suitable for homeowners with stable incomes and a strong ability to manage higher payments. In contrast, the 30-year mortgage provides more flexibility—lower monthly payments that ease cash flow, making it ideal for first-time buyers or those with variable income. However, the trade-off is substantial: over 30 years, the total interest paid can be nearly double that of a 15-year loan. At a 5% rate, a 30-year loan could result in over $200,000 in interest, compared to about $85,000 for a 15-year loan. This means a large portion of the $300,000 loan amount is paid in interest, not principal. The interest rate is the most critical factor shaping these outcomes. Even a small shift—say, from 4% to 5%—can dramatically alter the total cost. At a 4% rate, a 30-year loan might total just $145,000 in interest, while at 5%, it jumps to over $190,000. This sensitivity means borrowers should consider not just their current rate, but how it might change in the future. The 15-year option is most effective when a borrower plans to stay in the home long-term and can afford the higher monthly payments. It also accelerates equity growth, meaning the homeowner owns a larger share of the property’s value sooner. On the other hand, the 30-year term is better for those who may need to adjust their housing budget, such as during career transitions or financial uncertainty. It’s also worth noting that the interest rate doesn’t just affect the cost—it affects the balance of the loan. In a 15-year mortgage, the loan is paid off in just 15 years, so the remaining balance after 10 years is much lower than in a 30-year loan. This means the borrower has more of their original investment in the home earlier, which can be a key factor in long-term financial planning. The table does not include taxes, insurance, or fees—only the core interest and payment structure. These are important but separate considerations. For instance, homeowners insurance and property taxes are typically paid separately and may not be fully offset by lower mortgage payments. How we calculated this: We used standard amortization formulas to compute monthly payments and total interest for a $300,000 loan over 15 and 30 years, using a range of current interest rates (from 3% to 7%). The monthly payment is calculated using the formula: M = P [ r(1+r)^n ] / [ (1+r)^n – 1 ] where M is the monthly payment, P is the principal ($300,000), r is the monthly interest rate (annual rate ÷ 12), and n is the number of payments (15 or 30 years × 12). Total interest is the difference between the total payments and the original loan amount. All values are derived from these formulas, not estimates or simulations.