15 vs 30-Year Mortgage: Which Actually Saves You More?

The 15-versus-30-year choice is the biggest single decision in a mortgage — bigger than shopping a quarter-point of rate. One term roughly halves your lifetime interest; the other keeps several hundred dollars a month in your pocket. Here is the real math, and the third option most borrowers never price.

The headline numbers

Take a $280,000 loan. Thirty-year loans currently price around 6.5%; fifteen-year loans typically run about half a point lower, so call it 6.0%:

	30-year @ 6.5%	15-year @ 6.0%
Monthly principal & interest	~$1,770	~$2,363
Total interest paid	~$357,000	~$145,000
Interest saved	—	~$212,000

Two forces produce that enormous gap: the shorter loan simply has half as many months for interest to accrue, and lenders reward the lower risk with a better rate. Note the numbers above are principal and interest only — your real payment adds taxes, insurance and possibly PMI, which is why it is worth running your own figures through the mortgage calculator with the full PITI breakdown.

What the comparison hides

The 15-year loan is not “cheaper.” It costs ~$590 more every month, mandatorily. That money has an opportunity cost:

• It cannot build your emergency fund.
• It cannot capture an employer 401(k) match (an instant 50–100% return that beats any mortgage math).
• It cannot pay down credit cards at 24% APR — which should always come first, as the debt payoff calculator will make obvious.
• And if your income stumbles, the higher payment is not optional. Missing mortgage payments has consequences that missing investment contributions does not.

The honest framing: the 15-year term is a forced savings program with a great interest rate and no flexibility. Whether that trade suits you depends on how secure your income is and what else your money could be doing. Investors with long horizons often note that historical stock returns exceed 6% — the counter-argument is that a guaranteed 6% (interest avoided) is worth more than a hoped-for 8%. See the math of that comparison in our compound interest guide.

The third option: a 30-year loan paid like a 15

Take the 30-year term, then voluntarily pay the 15-year amount. Extra payments go straight to principal, so the result lands remarkably close to the true 15-year loan — in our example, paying ~$590 extra monthly on the 30-year loan pays it off in roughly 17 years and saves about $170,000 of the $212,000 gap.

What you give up: the half-point rate discount (that’s the ~$40k difference). What you keep: the right to stop. Lose a job, face a medical bill, want to redirect money to a better opportunity — you drop back to the lower required payment with a phone call to nobody. For most households that optionality is worth the price.

Model your own version in the mortgage calculator: set the 30-year term, then put any amount in the extra-payment field and read the years-saved and interest-saved lines. Even $100–200 a month moves the numbers more than most people believe — the full mechanics are in the mortgage calculator guide.

A quick decision framework

• Choose 15 years if the payment fits under ~28% of gross income with room to spare, your emergency fund is funded, and you already capture every retirement match.
• Choose 30 years, pay extra if you want the same trajectory with an escape hatch — the default recommendation for most.
• Choose 30 years, minimum payment if the alternative use of the money is genuinely better: high-APR debt elimination, matched retirement money, or a thin emergency fund.

Bottom line: the 15-year loan wins the interest math; the 30-paid-like-15 wins the real-life math. Whichever you lean toward, decide with your own numbers — not the lender’s brochure.