The True Cost of a 30-Year vs 15-Year Mortgage Across U.S. Metros

At this week's average mortgage rates, financing the typical American home with a 30-year loan instead of a 15-year one costs an extra $227,471 in interest — while saving the buyer about $603 a month. In the priciest metro we studied, San Jose, that same choice adds nearly $1 million in lifetime interest. We ran the math on a 20%-down conventional mortgage across 17 major U.S. metros to show exactly what the longer term costs, where, and why the gap is so consistent.

Mortgage rates sit in the mid-6% range and home values remain near all-time highs, which makes the term decision more consequential than it was in the 3%-rate era of a few years ago. When money was nearly free, the gap between a 30- and 15-year loan was modest; at today's rates, the longer term's compounding interest is punishing. Yet the 30-year remains the default for the overwhelming majority of buyers — almost always for the lower monthly payment. This study isn't an argument against that choice. It's an attempt to price it honestly, so the trade-off is a decision rather than a default.

Key findings

Five numbers capture the whole study. Each is computed from the same two public inputs — current Freddie Mac average rates and Zillow's typical-home-value estimate for each metro — run through a standard fixed-rate amortization formula.

How we calculated this

This study deliberately uses no proprietary or private data. Every figure comes from two free, widely cited public sources and one piece of math, so anyone can reproduce it.

Mortgage rates. We used the Freddie Mac Primary Mortgage Market Survey for the week ending June 18, 2026: a 30-year fixed averaging 6.47% and a 15-year fixed averaging 5.81%. PMMS reports rates for conventional, conforming loans for borrowers with strong credit putting 20% down — the same borrower profile we model.

Home values. For each metro we used the Zillow Home Value Index (ZHVI) for May 2026 — a smoothed, seasonally adjusted measure of the typical home value (the 35th-to-65th-percentile range) for all home types. ZHVI is a typical-value estimate, not a record of actual sale prices, but it is the most consistently comparable cross-metro figure available for free.

The formula. Each loan is the standard closed-form fixed-rate payment, P×r×(1+r)ⁿ / ((1+r)ⁿ−1), with monthly compounding — the exact math behind our mortgage calculator, which we cross-check against Bankrate. Total interest is the sum of every payment minus the original loan.

Assumptions. We hold these constant across every metro so the comparison is clean:

• 20% down payment, so the financed loan equals 80% of the home value.
• Conventional fixed-rate loan, U.S. monthly compounding, no points and no extra payments.
• Principal and interest only — property taxes, homeowners insurance, HOA dues, and PMI are excluded (PMI generally does not apply at 20% down anyway).
• Both terms priced at the same week's average rate, so the only variables are term length and loan size.

We chose these inputs for comparability and reproducibility. Freddie Mac's survey is the most-cited U.S. rate benchmark, and ZHVI is published for every metro on a consistent monthly basis, so the cross-metro comparison is apples-to-apples. Holding the down payment, rate week, and loan structure identical isolates exactly what we're measuring: how term length and home price drive interest cost. Every number below can be reproduced from those two public sources and a standard amortization formula.

The national picture

Start with the typical American home. At a ZHVI of $370,320 and 20% down, the buyer finances $296,256. The 30-year loan costs $1,867 a month and $375,755 in total interest. The 15-year loan costs $2,470 a month — $603 more — but only $148,284 in interest. Stretching the same loan over an extra 15 years more than doubles the interest, from $148,284 to $375,755.

Put another way: over 30 years, the typical buyer pays 127% of the original loan amount back in interest alone, on top of repaying the principal. Over 15 years, interest is just 50% of the loan. The longer you borrow, the more of the early years go almost entirely to interest rather than principal.

That is amortization front-loading at work. On the national 30-year loan, the very first monthly payment splits into $1,597 of interest and just $269 of principal — roughly 85% of your entire first year goes to interest rather than equity. A 30-year loan doesn't reach the tipping point where each payment puts more toward principal than interest until year 20. A 15-year loan crosses that line within its first few years, which is exactly why it builds equity faster and accrues so little total interest.

Metro by metro

The national average hides enormous variation. Because the interest gap scales with loan size, it explodes in expensive markets. In San Jose (ZHVI $1,610,466), a 20%-down buyer finances $1,288,373 — and pays $1,634,104 in interest over 30 years versus $644,866 over 15. The gap is $989,238, almost the price of a second home. San Francisco ($705,912), Los Angeles ($594,973), and San Diego ($581,310) all clear half a million dollars in extra interest.

At the other end, even the most affordable metros carry six-figure gaps. Pittsburgh — the cheapest market we studied at a $231,356 typical value — still shows a $142,112 difference. Cleveland ($154,921) and Detroit ($165,284) are close behind. There is no U.S. metro where the term choice is a rounding error.

Three regional patterns stand out. Coastal California is its own tier — San Jose, San Francisco, Los Angeles, and San Diego each carry a gap above $580,000, more than double the national figure. The coastal Northeast and Pacific Northwest (Seattle, Boston, New York) cluster in the $447,000–$461,000 range. The Sun Belt and large Midwest metros — Denver, Miami, Phoenix, Austin, Dallas, Minneapolis, and Chicago — span roughly $217,000 to $352,000, bracketing the national gap, while the Rust Belt (Detroit, Cleveland, Pittsburgh) sits lowest at $142,000–$165,000. The ranking tracks home prices almost perfectly — which is the whole point: the term you choose is a price multiplier, not an independent lever.

Why the gap is so consistent

Here is the part that surprises people. Although the dollar gap swings from $142,112 in Pittsburgh to $989,238 in San Jose, the gap as a share of the home's value is almost identical everywhere: right around 61%. Run the ratio for any row in the table and you land in the same place — San Jose's $989,238 gap is 61% of its $1.61M value; Pittsburgh's $142,112 gap is 61% of its $231K value.

That is not a coincidence. The interest a loan accrues, relative to its size, is fixed entirely by the interest rate and the term — not by how big the loan is. At 6.47% over 30 years, every dollar borrowed costs about $1.27 in interest; at 5.81% over 15 years, about $0.50. The difference, roughly $0.77 per dollar of loan (about $0.61 per dollar of home value at 20% down), holds in every market. Expensive metros don't get a worse deal on the term trade-off — they just write a bigger check, because the same percentage is taken on a much larger number.

This is also why the choice matters most exactly where homes cost most. A one-percentage-point difference in rate, or a 15-year-shorter term, is invisible as a percentage but life-changing as a dollar figure when the loan is seven figures.

Why a 15-year charges less, twice over

The 15-year loan wins on interest for two reasons that compound. First, you borrow for half as long, so interest has far less time to accrue. Second, lenders price 15-year loans at a lower rate — this week, 5.81% versus 6.47%, a 0.66-percentage-point discount. A shorter loan carries less duration risk for the lender (their money is exposed to rate moves and default risk for fewer years), and that lower risk is passed through as a lower rate. So the 15-year borrower pays a smaller percentage for fewer years, and the two effects multiply rather than add. That is why halving the term doesn't merely halve the interest — nationally it cuts it by more than 60%, from $375,755 to $148,284.

What this means for buyers

The 30-year mortgage is popular for a sound reason: the lower payment buys breathing room and qualifying power. Nationally, the 15-year payment is $603 a month higher; in San Jose it is $2,622 higher ($10,740 vs $8,118). Many households simply cannot carry the 15-year payment, and stretching to do so at the expense of an emergency fund or retirement contributions is its own risk.

But the lifetime cost of that flexibility is steep, and our data quantifies it precisely. The 15-year borrower isn't just paying off the house faster — they are buying at a lower rate (5.81% vs 6.47% this week) and paying interest for half as long. Both effects compound, which is why the interest more than doubles rather than simply scaling with the extra years.

There is also a well-known middle path: take the 30-year loan for the payment flexibility, then make extra principal payments when you can. You keep the lower required payment as a safety valve but shorten the effective term voluntarily. The catch is the rate — you still borrow at the higher 30-year rate, so a self-accelerated 30-year never fully matches a true 15-year on interest. Our mortgage recast and mortgage calculators let you model exactly how much an extra $200 or $500 a month would save on your own numbers.

When a 15-year makes sense

• You can comfortably carry the higher payment and still fund retirement and an emergency fund.
• You value being debt-free sooner — especially if the payoff lands near retirement.
• You want the lower rate and are confident in your income stability.

When a 30-year makes sense

• The lower required payment is what makes the home affordable or keeps your budget resilient.
• You expect to invest the monthly difference and believe you can beat your mortgage rate after tax.
• You may move or refinance before the longer term's interest fully accrues.

The "invest the difference" counterargument

The strongest case for the 30-year isn't a lower lifetime cost — it's opportunity cost. Take the 30-year, the argument goes, and invest the $603 a month you're not sinking into a 15-year payment. Whether that beats the 15-year comes down to a single comparison: your after-tax investment return versus your mortgage rate. Paying the loan down is a guaranteed 6.47% return — every dollar of principal you retire is interest you never owe. To win by investing instead, your portfolio has to clear roughly 6.47% after taxes and fees, reliably, across the whole term. A diversified stock portfolio has historically done better than that over long horizons — but not without steep drawdowns, and never with a guarantee. The 15-year is the lower-risk, lower-return path; "invest the difference" is the higher-risk, potentially-higher-return one. Neither is free money, so treat it as a risk decision, not an arithmetic certainty. You can pressure-test your own assumptions in our compound interest calculator.

The bottom line

The 30-year mortgage trades a lower monthly payment for a much higher lifetime cost, and this study puts hard numbers on that trade at mid-2026 rates. For the typical American home it's $227,471 in extra interest in exchange for $603 a month of breathing room; in the most expensive metros the extra interest approaches or exceeds the price of a whole house. The percentage is remarkably stable — about 61% of a home's value — because it's set by the rate and the term, not the price. None of this makes the 30-year wrong: for most buyers the lower payment is the difference between owning and not, and the monthly savings can be invested or kept as a cushion. But buyers deserve to see the full price tag of the longer term, not just the smaller payment — and now they can, for their own metro and their own numbers.

Frequently asked questions

Is a 15-year mortgage always the better choice?

No. On interest alone it wins decisively — $227,471 nationally — but it costs $603 more every month, and far more in expensive metros. It's the better choice only if you can carry the higher payment without shortchanging your emergency fund or retirement savings. For many households the 30-year's lower required payment is what makes the home affordable at all, and that flexibility has real value.

Why is the 15-year interest rate lower than the 30-year?

Lenders take on less risk over a shorter term — their capital is exposed to interest-rate moves and default risk for fewer years — so they charge less for it. This week that discount is 0.66 percentage points (5.81% vs 6.47%). The lower rate is a second reason the 15-year accrues so much less interest, on top of the shorter borrowing period.

Does the interest gap shrink if mortgage rates fall?

Lower rates shrink the absolute dollar gap, but the structure holds. As long as 15-year loans are priced below 30-year loans and amortization front-loads interest, the longer term will cost dramatically more — and the gap will remain a large share of the home's value. Re-run the numbers at today's rate in our mortgage calculator to see your figure.

Can I get a 15-year's savings on a 30-year loan?

Partly. Take the 30-year for the lower required payment, then make extra principal payments to shorten the effective term. You keep the flexibility to drop back to the smaller payment if money gets tight. The catch is the rate: you still borrow at the higher 30-year rate, so a self-accelerated 30-year never fully matches a true 15-year on total interest.

Does the mortgage interest deduction change the math?

For most households, no. The vast majority now take the standard deduction and never itemize mortgage interest at all. Even for those who do itemize, the deduction only refunds a fraction of the interest paid — deliberately paying more interest to capture a partial tax break is rarely a net win.

Limitations

A few caveats keep this honest. First, ZHVI is a typical-value index, not a median sale price or an appraisal of any specific home; metro figures are directional, not a quote for your purchase. Second, mortgage rates move weekly — the 0.66-percentage-point spread between the 30- and 15-year averages is typical but not fixed, and a wider or narrower spread changes the gap. Third, we model principal and interest only; taxes, insurance, and HOA dues are real costs but are identical across the two terms, so excluding them doesn't affect the comparison. Finally, we assume the loan is held to term with no extra payments or refinancing; in reality the median mortgage is paid off or refinanced well before maturity, which reduces the interest actually paid on both terms.

Sources

• Freddie Mac, Primary Mortgage Market Survey (PMMS) — 30-year fixed 6.47%, 15-year fixed 5.81%, week ending June 18, 2026.
• Zillow Research, Zillow Home Value Index (ZHVI), all homes, smoothed & seasonally adjusted — metro typical home values, May 2026 (series: Metro_zhvi_uc_sfrcondo_tier_0.33_0.67_sm_sa_month).
• Calculover, mortgage calculator — the fixed-rate amortization formula used for all payment and interest figures, cross-checked against Bankrate.