The 30-year fixed is America's default mortgage for a reason: it makes the payment manageable. The 15-year fixed is the perennial challenger for a different reason: it makes the loan cheap. Choosing between them is really a choice about what you want your monthly budget — and the next decade and a half — to look like.

The trade, in real numbers

Two things favor the 15-year: you borrow the money for half as long, and lenders charge less for it — 15-year rates typically run well over half a percentage point below 30-year rates. With posted 30-year rates clustered in the mid-6s in early September 2026, here is the trade on a $400,000 loan, using 6.5% for the 30-year and 5.75% for the 15-year as illustrative rates:

  • 30-year at 6.5%: about $2,528 a month in principal and interest — and roughly $510,000 of total interest over the life of the loan.
  • 15-year at 5.75%: about $3,322 a month — and roughly $198,000 of total interest.

That is the whole bargain in two lines: about $793 more per month buys back roughly $312,000 in interest, plus outright ownership of your home fifteen years sooner. Interest genuinely costing something is what makes this comparison so much starker than it looked in the 3% era.

The case for the 30-year anyway

The 15-year's math only works if you can carry the payment through your worst year, not your best one. The 30-year's lower obligation is a form of insurance: job loss, a new baby, a roof, a recession — the smaller required payment is easier to defend. And the difference can be put to work elsewhere. If you carry credit card debt at 20%-plus or have not filled tax-advantaged retirement space, those uses beat prepaying a 6.5% mortgage. A dollar of required payment is a commitment; a dollar of optional extra is a choice.

The middle path: take the 30, pay it like a 15

Nothing stops you from taking the 30-year and sending the 15-year-sized payment anyway. Extra principal shortens the loan dramatically, and the moment life gets expensive you can drop back to the required payment with no penalty and no phone call. You will pay somewhat more than a true 15-year — the rate is higher, and most people's discipline leaks — but you keep the flexibility, which is exactly what the 15-year takes away. If you go this route, confirm your loan has no prepayment penalty (almost none do today) and that extra payments are applied to principal.

How to decide

  • Choose the 15-year if the payment fits under roughly a quarter of your gross income, your emergency fund is fully built, and you are already saving for retirement. You are buying a guaranteed return equal to your rate, and a paid-off house before many people's kids finish school.
  • Choose the 30-year if the 15-year payment would crowd out retirement savings, your income is variable, or you value the option to redirect money as life changes.
  • Refinancers: if you are years into a 30-year, refinancing into a 15 avoids the classic trap of restarting the 30-year clock and re-amortizing your progress away.

There is no universally right answer — there is the loan that fits the budget you actually live on. Run your own balance through the same arithmetic before you commit; the spread between lenders on any given morning is wide enough that shopping the rate matters as much as picking the term.