15 vs 30 Year Mortgage: The Full Cost Breakdown
The 30-year mortgage is America's default — but the 15-year saves you hundreds of thousands in interest. The question isn't which is cheaper overall. It's which fits your cash flow, goals, and risk tolerance.
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The Numbers Don't Lie
On a $400,000 loan at today's rates (approximately 6.5% for 15-year, 7.0% for 30-year), you'll pay over $330,000 more in interest with a 30-year mortgage. That's not a rounding error — that's a second home.
But the 30-year also gives you $825/month back in cash flow. That money, invested in the market, could grow significantly. The right answer depends on what you do with the difference.
Side-by-Side Scenarios
The Rate Advantage of 15-Year Loans
Lenders charge less for 15-year mortgages — typically 0.5% to 0.75% lower than 30-year rates. Why? Less risk. You pay them back faster, so there's less time for you to default or for the economy to shift.
This rate differential compounds the savings. On a $400k loan, that 0.5% rate difference alone saves roughly $80,000-$90,000 in interest — before you even account for the shorter loan term.
Pros & Cons
15-Year Mortgage
PROS
- ✓Lower interest rate
- ✓Massive interest savings over life of loan
- ✓Build equity twice as fast
- ✓Debt-free 15 years sooner
- ✓Forced financial discipline
CONS
- ✗Higher monthly payment
- ✗Less cash flow flexibility
- ✗Harder to qualify
- ✗Less money for other investments
30-Year Mortgage
PROS
- ✓Lower monthly payment
- ✓More cash flow for investing
- ✓Easier to qualify
- ✓Payment flexibility (can pay extra)
- ✓Inflation erodes the real cost over time
CONS
- ✗Pay far more interest over time
- ✗Higher interest rate
- ✗Slower equity build
- ✗Debt until your late 50s–60s
Which Is Right for You?
Choose 15-year if:
You can comfortably afford the higher payment (the rule: keep housing under 28% of gross income), you prioritize being debt-free, and you're closer to retirement. The guaranteed 6.5% return of paying off debt is often better than speculative investment returns.
Choose 30-year if:
Cash flow is tight, you have high-interest debt to eliminate first, or you're disciplined investors who will actually invest the monthly difference. A 30-year mortgage with extra principal payments can beat both options.
The hybrid approach:
Get a 30-year mortgage but make 15-year payments. You get the flexibility (if income drops, revert to minimum) with much of the savings of a 15-year. Use our mortgage payoff calculator to model this exact strategy.