Mortgage Types Compared: Fixed vs ARM, 15 vs 30, Conforming vs Jumbo

Loan officers hand you a menu with four or five options on it and then ask which one you want, as if you'd been studying for this. You haven't. And the differences between them are not cosmetic — picking a 15-year over a 30-year on the same house changes your monthly payment by roughly $800 and your lifetime interest by roughly $319,000.

There are only three questions on the menu, and they're independent of each other. How long is the term? Is the rate fixed or adjustable? Is the loan size inside the conforming limit or outside it? Answer those three and you've picked your mortgage.

Question one: fixed or adjustable

A fixed rate is set at closing and never moves. An adjustable rate is fixed for an initial period — a few months, a year, several years — and then resets on a schedule for the rest of the term. The CFPB is blunt about what that means: with an ARM, "your monthly principal and interest payment could go up a lot, even double."

After the initial period, an ARM's rate is built from two pieces: an index that moves with the market, and a margin the lender adds on top. The index is out of everyone's control. The margin is fixed for the life of the loan and it is the number that follows you forever, so ask what it is before you ask anything else about the loan.

Three caps limit how far the rate can travel. The initial adjustment cap governs the first reset, and the CFPB says it's commonly either two or five percentage points. The subsequent adjustment cap governs each reset after that — most commonly one or two points. The lifetime cap governs the total move, most commonly five points. Add the lifetime cap to your starting rate and that is the worst case you have agreed to.

Here's the test that matters: run the payment at your starting rate plus the lifetime cap. If you can't pay that number on today's income, the loan is not affordable, no matter what the teaser rate says. The CFPB's own warning is worth reading twice — "Don't assume you'll be able to sell your home or refinance your loan before the rate changes." That assumption is exactly what broke a generation of borrowers in 2007.

An ARM genuinely suits a narrow group: people with a firm, external, non-negotiable reason to be out of the house before the first reset. Military orders with a known rotation date. A residency that ends on a calendar. A job contract with a term. "We'll probably move in a few years" is not that reason.

For nearly everyone else, fixed. Between 2008 and 2022, per CFPB data, fixed-rate loans were chosen by 85 to 95 percent of buyers, and that's not herd behavior — it's people correctly deciding that a stable payment is worth more to them than a discount that expires.

Question two: 15 years or 30

Shorter terms carry lower rates and much higher payments. In Freddie Mac's Primary Mortgage Market Survey for the week of August 20, 2026, the 30-year fixed averaged 6.65% and the 15-year averaged 5.95%.

Run $400,000 through both:

1. 30 years at 6.65%: principal and interest of about $2,568 a month. Over 360 payments, that's roughly $924,400 paid in — about $524,400 of it interest.
2. 15 years at 5.95%: about $3,365 a month. Over 180 payments, roughly $605,600 paid in — about $205,600 of interest.
3. The 15-year costs about $797 more every month and saves roughly $319,000 in interest.

That looks like an obvious win until you notice what the 15-year actually does: it takes $797 a month of your flexibility and locks it in a contract. Lose your job in year four and the 30-year borrower cuts back; the 15-year borrower has a payment they can't cut.

The move most people should make instead is to take the 30-year and pay it like a 15-year voluntarily. You give up the rate discount — about 0.70 points at current survey rates — but you keep the right to stop. On a $400,000 loan, paying an extra $797 a month against principal on the 30-year gets you most of the interest savings with an escape hatch. Confirm with your servicer that extra payments are applied to principal, not held as a prepaid next installment, because some servicers do the second thing by default.

Take the actual 15-year when the payment is comfortable at your current income with room to spare, when you're within striking distance of retirement and want the thing gone, or when you know from experience that money you don't commit is money you spend.

Question three: conforming, jumbo, or government-backed

"Conforming" means the loan fits inside the limits Fannie Mae and Freddie Mac will buy. That's a plumbing detail that turns into a pricing detail: conforming loans are easier to sell into the secondary market, so they usually price better and underwrite to published standards.

The limits change every single year, which is why any article quoting one without a date is useless to you. FHFA set the 2026 baseline for one-unit properties at $832,750, up $26,250 from 2025, an increase driven by a 3.26% rise in its house price index between the third quarters of 2024 and 2025. High-cost counties get up to a ceiling of $1,249,125 — 150% of the baseline. Alaska, Hawaii, Guam, and the U.S. Virgin Islands start at that $1,249,125 figure and top out at $1,873,675. Your county's number is on FHFA's published county list, and it is the only number that matters to you.

Cross the limit and you're in jumbo territory: a loan held on a lender's own books or sold privately, underwritten to that lender's appetite rather than to a public rulebook. Expect larger down payments, deeper reserve requirements, and much wider pricing variation between lenders — which cuts both ways. Shopping matters more on a jumbo than on anything else, because there's no standard to anchor to.

There's a trick worth knowing at the boundary. If your loan lands just above the limit, a slightly larger down payment can drop you back under it and into conforming pricing. On a $860,000 loan in a baseline county, finding another $27,250 of down payment gets you to $832,750 and changes which market your loan lives in.

The government-backed lane

FHA, VA, and USDA loans aren't a separate rate structure so much as a separate underwriting structure, aimed at borrowers conventional underwriting turns away.

• FHA: low down payment, and available at credit scores conventional underwriting won't touch. Mortgage insurance is the trade, and on a low-down-payment FHA loan it runs for the full mortgage term rather than cancelling. This site's FHA versus conventional comparison has the credit thresholds and the thirty-year cost difference.
• VA: for eligible veterans, service members, and surviving spouses. VA states plainly that the program "doesn't require down payments or monthly mortgage insurance." There's a funding fee instead — 2.15% of the loan on a first-use purchase with less than 5% down, 1.5% with 5% down, 1.25% with 10% down — and veterans receiving compensation for a service-connected disability are exempt from it entirely.
• USDA: for low- to middle-income buyers in eligible rural areas, with geography and income both gating eligibility.

If you're a first-time buyer, run the state housing finance agency programs alongside these before you commit — this site's first-time homebuyer programs article covers what's stacked on top and how to find yours.

The comparison nobody makes correctly

People compare mortgages by interest rate. Rate is one input. Compare Loan Estimates instead — the standardized form every lender has to produce for you. It puts rate, points, origination charges, and total five-year cost on the same page in the same boxes at every lender, which is precisely why the form exists.

Get at least three, on the same day, for the same loan amount and term. Mortgage inquiries inside a 45-day window are recorded on your credit report as a single inquiry, so there's no credit cost to shopping properly.

Don't buy the payment

The single worst way to choose a mortgage is to pick whichever product produces a monthly number you can just barely stand. That's how people end up in ARMs they can't survive the reset of, and in 30-year loans on houses priced for a 15-year budget. Principal and interest is also not your payment — taxes and insurance ride along in escrow and they move every year, as this site's escrow shock article walks through in unpleasant detail.

Pick the term first, based on what you can pay without flinching. Pick fixed unless you have a date on a calendar. Then check your county's conforming limit and see which side of it you're on. That's the whole decision, and it takes an afternoon.