Fixed vs adjustable rate mortgage is a bet on how long you will keep the loan. Work out the break-even and the answer usually settles itself.
Written by Renzo Johnson, Licensed Mortgage Loan Originator · Last updated: August 2026
Fixed vs adjustable rate mortgage in one table
| Fixed rate | Adjustable rate | |
|---|---|---|
| Payment | Identical for the full 15, 20 or 30 years | Fixed for 5, 7 or 10 years, then adjusts annually |
| Starting rate | Higher | Typically 0.5% to 1.0% lower |
| Risk | You carry none | You carry it, limited by the caps |
| Suits | Staying ten years or more | Selling or refinancing inside the fixed period |
Price the discount, then price the ceiling
The ARM discount is real money, so start by measuring it. On a $400,000 loan, a rate 0.75% lower saves roughly $190 a month. Across a five-year fixed period that is about $11,400 you keep.
Then measure the other side. Your caps define the worst case, and they are usually written as three numbers such as 2/1/5. The first limits the initial adjustment, the second limits each later one, and the third limits the lifetime increase. A 5.5% start with a lifetime cap of 5 means the rate can reach 10.5%, which on that same loan is roughly $3,659 a month against $2,271 at the start.
Therefore the question is not whether rates will fall. It is whether you could pay the capped figure if they do not. If the answer is no, the $11,400 is not a saving. It is a deposit on a risk you cannot cover.
The plan that usually fails
Most ARM borrowers intend to refinance before the first adjustment. Often that works, and it depends on three things holding: you still qualify, the property still appraises, and rates cooperate.
Florida adds a specific pressure. Insurance premiums feed the ratio a lender uses, and they have risen sharply. Consequently a borrower who qualified easily in year one can fail the same test in year six on identical income, purely because the windstorm premium doubled. Treat refinancing as a good outcome rather than the plan.
When an ARM genuinely fits
- Military families on three to five year assignment cycles, who often sell before the first adjustment
- Seasonal residents buying a second home they expect to sell within a decade
- Buyers with a firm, dated reason to move rather than a general intention
- Anyone who could absorb the capped payment without distress
If none of those describe you, take the fixed rate and stop thinking about it. Read how ARM caps work in detail, or compare 15-year against 30-year terms instead.
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Payment figures above are illustrative and assume the rates stated. Caps, index and margin vary by loan, so read your own Loan Estimate. The CFPB explains ARM rate caps in plain language.