15-Year vs 30-Year Mortgage: The Real Cost of the Same Loan

The choice between a 15-year and a 30-year mortgage is really a choice between two costs: a higher payment every month, or a much higher total over the life of the loan. On a $320,000 loan, the 15-year option costs about $2,666 a month, the 30-year about $2,023. That extra $643 a month on the 15-year buys you something big: roughly $248,283 less interest by the time the house is paid off.

The “better” marks are split, which reflects the real trade-off. The 30-year wins on the one number you feel every month, the payment. The 15-year wins on almost everything else: far less interest, a lower rate, and a house you own outright in half the time.

Why the 15-year saves so much

Two things stack up in its favor. First, you are borrowing the money for half as long, so there is simply less time for interest to pile up. Second, lenders usually charge a lower rate on a 15-year loan because it is less risky for them, which is why the example uses 5.8% against 6.5%. Put those together and the interest saved is not a small number. It is often more than a year of take-home pay.

Why plenty of people still choose the 30-year

The 30-year is the more flexible choice. That lower payment leaves room in the budget for retirement savings, an emergency fund, or just breathing space when life gets expensive. You can also take a 30-year mortgage and pay it like a 15-year whenever you want, by sending extra toward the principal. That keeps your required payment low but lets you attack the loan in good months. The reverse is not true. A 15-year locks you into the higher payment whether the month is good or not.

How to choose

A simple way to decide: figure out the 15-year payment first, then ask whether you could make it comfortably even in a tight month, while still saving for retirement and keeping an emergency fund. If yes, the 15-year is hard to beat on the math. If the payment would leave you stretched, take the 30-year and pay extra when you can. The worst outcome is a 15-year payment you cannot sustain, because missing a mortgage payment is far more costly than the interest you were trying to save.

Run your own price, down payment, and rate with the Mortgage Calculator, and see how extra payments change the picture with the Mortgage Extra Payment Calculator.