Term length is the second-biggest financial decision in a mortgage after the interest rate, and it has nothing to do with negotiation — you simply pick. The 30-year fixed is the default in the U.S. (about 90% of new originations), but the 15-year fixed deserves consideration for buyers with the income to support it. The right answer is rarely obvious, and it's rarely the same answer for two different households.
The Fundamental Tradeoff
A 15-year mortgage trades higher monthly payments for vastly lower lifetime interest. A 30-year mortgage trades total cost for monthly affordability and flexibility. The two structures are designed for different financial situations, not different financial sophistication — neither is "smarter."
Two adjustments work in the 15-year's favor beyond just the shorter term: lenders price 15-year loans at roughly 0.5%–0.75% below 30-year loans (less duration risk for them), and the faster principal paydown means less interest accrues regardless of rate.
Real Numbers on a $400,000 Loan
Assuming current rates (30-year fixed at 6.50%, 15-year fixed at 5.85%) on a $400,000 loan:
Paying $813 more per month for 15 years saves you $308,775 in interest and pays off your home twice as fast.
| Metric | 30-Year @ 6.50% | 15-Year @ 5.85% |
|---|---|---|
| Monthly payment (P&I) | $2,528 | $3,341 |
| Total interest paid | $510,178 | $201,403 |
| Total cost of loan | $910,178 | $601,403 |
| Years to be debt-free | 30 | 15 |
| Total interest savings (15-yr) | — | $308,775 |
When the 15-Year Wins
- Your gross household income easily covers the higher payment with margin for emergencies (28% rule still passes).
- You're already maxing tax-advantaged retirement accounts (401k, IRA, HSA) — extra mortgage paydown is reasonable.
- You're within 15 years of a retirement goal and want to enter retirement debt-free.
- You value the psychological certainty of a faster payoff over flexible cash flow.
- Mortgage rates are high enough that the interest savings are dramatic.
When the 30-Year Wins
Take the 30-year mortgage but voluntarily pay it on a 15-year schedule. You get the lower required payment for safety, but you build equity at the 15-year pace. The catch: you'll pay the 30-year's higher rate, so you'll be ~$30k–$60k behind a true 15-year payoff. Whether the flexibility is worth that cost is your call.
- The 15-year payment would push your housing cost above 28% of gross income.
- You haven't fully funded retirement accounts — the 30-year keeps cash available for higher-return investments.
- You expect significant income growth and may refinance or move within 7–10 years.
- You want the flexibility to make extra payments voluntarily without the obligation of the higher monthly amount.
- You have other debts (student loans, high-interest cards) with rates higher than your mortgage rate.
The Middle Ground: 20-Year and Biweekly
A handful of lenders offer 20-year fixed mortgages, which split the difference: lower payment than 15-year, less total interest than 30-year, mid-tier rate pricing. They're less common but can be ideal for borrowers who want the 15-year discipline without the 15-year payment shock.
Biweekly payment programs (paying half your monthly amount every two weeks) effectively turn a 30-year into a 26-year payoff with no rate change. The trick is the 13th annual payment that biweekly schedules create. You can do this yourself by making one extra principal-only payment per year without enrolling in any program — same result, no fees.
The 15-year vs 30-year decision comes down to whether the monthly payment difference is comfortable income-wise AND whether the alternative use of that cash (retirement savings, business, other investments) would earn more than your mortgage rate. For most borrowers under 6.5% mortgage rates and with retirement underfunded, the 30-year wins; for borrowers above 6.5% rates with maxed retirement accounts, the 15-year wins. Model both scenarios in the Mortgage Calculator with your real income and see which payment fits without strain.
