$270,854. That's what choosing a 15-year mortgage at today's rates saves over a 30-year loan on a $360,000 balance. A quarter million dollars. It sounds like a no-brainer — and in a straight math comparison, it absolutely is.
But here's what most articles on this topic skip: you only realize that savings if you stay in the home for all 15 years, don't refinance, don't face an income disruption, and couldn't have invested the $742/month payment difference at a return higher than 5.75%. Change any one of those conditions and the math shifts — sometimes dramatically. In some scenarios, the 30-year borrower who invests the difference comes out ahead.
The Numbers, Plainly Stated
According to the Freddie Mac Primary Mortgage Market Survey (via FRED), the 30-year fixed rate as of March 26, 2026 is 6.38%. The 15-year fixed is 5.75%. That 63 basis point spread is notably wider than the historical average of 40–50 bps — a detail we'll come back to, because it affects the decision in a non-obvious way.
For a $360,000 loan (20% down on a $450,000 home), here's what those rates actually mean over the life of the loan:
| Metric | 30-Year at 6.38% | 15-Year at 5.75% | Difference |
|---|---|---|---|
| Monthly P&I payment | $2,247 | $2,989 | +$742/mo (15yr higher) |
| Total interest paid | $448,959 | $178,106 | $270,854 savings (15yr) |
| Remaining balance at year 5 | $336,531 | $272,342 | 15yr ahead by $64,189 |
| Equity built at year 5 | $23,469 | $87,658 | 15yr builds ~$64K more |
| Paid off | Year 30 | Year 15 | 15 years sooner |
Source: Amortization calculations based on FRED/Freddie Mac PMMS rates as of March 26, 2026. Does not include taxes, insurance, or PMI.
The $270,854 interest savings figure is real and it's large. But notice the 5-year equity comparison: $87,658 vs. $23,469. That's actually the more practically useful number for most borrowers, because very few people think in 30-year windows. Most buyers will sell or refinance within 10 years — which means the "full" interest savings of the 15-year are theoretical for many of them.
The Three Things That Actually Determine the Right Answer
The comparison table above is the easy part. Here's where it gets real.
1. Payment Flexibility Has Dollar Value. The 30-year's lower payment isn't just convenience — it's financial insurance. At $2,247/month, the 30-year gives you a committed minimum payment with the option to pay more. The 15-year locks you into $2,989 — always, every month, for 180 months. A job disruption, medical event, or business setback hits much harder when your base housing obligation is $742/month higher. That optionality has real worth that the spreadsheet doesn't capture.
2. The "Invest the Difference" Math Is Closer Than You Think. If a borrower takes the 30-year and invests that $742/month difference into index funds earning a 7% annual return (the S&P 500's approximate historical average), the portfolio value after 15 years would be roughly $235,302. Compare that to the 15-year's interest savings of $270,854 — the gap narrows to about $35,000. At an 8% investment return, the gap closes further. At 10%, the invest-the-difference approach pulls ahead of the 15-year.
The honest take: most people don't actually invest the difference. They spend it. If you know yourself and you won't invest that $742, the 15-year's forced savings have real value. If you're a genuinely disciplined investor with a long-term track record — and you'll actually put that money into index funds every month — the 30-year plus invest strategy is surprisingly competitive.
3. The Current Rate Environment Has a Wrinkle. As we explained in our analysis of the two-engine rate model, the 30-year mortgage is currently priced at a 196 basis point premium over the 10-year Treasury yield — well above the historical norm of ~150 bps. This means some of today's mortgage rates reflect spread compression risk: if MBS spreads normalize over the next 12–24 months, 30-year rates could naturally fall 40–60 bps even without any Fed action.
A 30-year borrower locked in today at 6.38% could refinance into a 5.75%–5.90% environment in 18–24 months and capture a meaningful rate improvement. A 15-year borrower already at 5.75% has less room to benefit from that same spread compression. It's not a dealbreaker, but it's a factor that's specific to this rate environment and worth weighing.
"Consumers who can afford the 15-year fixed benefit from accelerated equity building and substantially lower interest costs over the life of the loan." — Freddie Mac Primary Mortgage Market Survey, 2026
Who Should Choose the 15-Year Right Now
The 15-year makes strong sense when income is stable, high, and ideally dual. If your household income is $150,000+ and the additional $742/month represents less than 8% of your take-home, the payment stress is manageable and the interest savings are real and realizable. It's also the right call if you're buying what you genuinely expect to be a forever home — if you're confident you'll stay 15+ years with no refinancing plans, you'll capture the full $270,854 advantage.
Nearing retirement is another strong 15-year indicator: a 58-year-old buyer who wants the home paid off before retirement at 73 has excellent alignment between the loan term and their life plan. Similarly, if you know yourself and know you won't invest the difference — that the $742 would otherwise drift into lifestyle spending — the 15-year's forced discipline has genuine value.
One more current-market note: the 63 basis point spread between the 30-year and 15-year (vs. the historical 40–50 bps) means the 15-year is priced attractively relative to its own history right now. If you're going 15-year, today is a comparatively good time to do it.
Who Should Stay with the 30-Year
The 30-year is clearly the right call if the $742 monthly difference creates genuine payment stress — buying near the top of your budget, reduced emergency fund, or scaled-back retirement contributions. These tradeoffs are real costs that the interest savings comparison doesn't account for.
Early-career buyers with strong income growth ahead are natural 30-year candidates: the payment that feels tight today at 30 years old is a much smaller percentage of income at 38. Meanwhile, the lower obligation preserves flexibility that compounds in value over time. Geographic mobility is another factor — if you're likely to move within 7–10 years, you won't capture the full interest savings of the 15-year anyway. A 30-year with 5-year equity isn't dramatically different from a 15-year when you're selling at year 7 regardless.
And if you're genuinely, demonstrably a disciplined investor — not aspirationally, but actually — the 30-year plus monthly index fund contributions is a legitimate wealth-building strategy that competes directly with the 15-year's forced savings advantage.
The Practical Framework
Stop treating this as a math problem and start treating it as a financial-behavior problem. The math clearly favors the 15-year. The right choice depends on income stability, investment discipline, your timeline in the home, and your personal psychology around financial flexibility versus forced savings.
Our opinionated guidance: if you can afford the 15-year payment comfortably — meaning the $742 extra per month doesn't require you to reduce your emergency fund, skip retirement contributions, or live paycheck-to-paycheck — take it. The interest savings are real, the equity build is powerful, and the discipline is automatic.
If the payment is even somewhat of a stretch, take the 30-year and commit to making extra principal payments when cash flow allows. The ability to underpay in a genuinely hard month — medical emergency, job loss, career transition — is worth more than most borrowers realize until they actually need it. You can always pay like a 15-year mortgage from a 30-year loan. You can't go the other direction.
For a deeper look at how rate environment signals affect your mortgage timing decisions, see our guide on rate education fundamentals — particularly the ongoing coverage of the MBS spread and what it means for where rates are headed.
