What Is a Fixed-Rate Mortgage?
A fixed-rate mortgage locks the interest rate for the entire loan term — typically 15 or 30 years. Monthly payments remain identical throughout, making budgeting straightforward and providing complete protection against rate increases.
Fixed rates are priced based on the 10-year US Treasury yield plus a spread that reflects mortgage prepayment risk and lender profit margin. When Treasury yields rise, fixed mortgage rates follow.
Fixed-rate mortgages eliminate interest rate risk entirely for the borrower. In a rising rate environment, locking in a fixed rate can save tens of thousands over the loan term.
What Is a Variable-Rate (ARM) Mortgage?
Adjustable-rate mortgages (ARMs) begin with a fixed introductory period — typically 5, 7, or 10 years — then adjust annually based on a benchmark index (SOFR, 1-year Treasury) plus a margin set by the lender. The 5/1 ARM adjusts every year after the initial 5-year fixed period.
Caps limit how much the rate can move: a typical 2/2/5 cap structure means the rate cannot rise more than 2% at first adjustment, 2% at any subsequent adjustment, and 5% above the initial rate ever.
Understanding ARM Caps
A 5/1 ARM starting at 6.1% with 2/2/5 caps can never exceed 11.1%. At first adjustment after 5 years, the maximum rate is 8.1%. Understanding caps transforms ARM risk from abstract to quantifiable.
Side-by-Side Comparison
| Feature | 30-yr Fixed | 15-yr Fixed | 5/1 ARM | 7/1 ARM |
|---|---|---|---|---|
| Initial Rate (2026) | 6.8% | 6.1% | 6.1% | 6.3% |
| Rate Certainty | 30 years | 15 years | 5 years | 7 years |
| Monthly Payment ($400K) | $2,617 | $3,390 | $2,440 | $2,492 |
| Rate Risk | None | None | After yr 5 | After yr 7 |
| Best For | Long-term owners | Rapid payoff | Short horizon | Medium horizon |
Break-Even Analysis
The choice between fixed and ARM depends on your time horizon. An ARM saves money if you sell or refinance before the rate adjusts significantly. The break-even point — where fixed and ARM total costs cross — is typically 7–10 years into a 30-year mortgage at current rate spreads.
- Plan to sell in <5 years — ARM is almost always cheaper; you capture the lower initial rate and exit before adjustments.
- Plan to hold 7–15 years — Depends on rate direction; ARM may or may not win depending on how rates move.
- Plan to hold 15–30 years — Fixed rate almost always wins on total cost certainty and protection against rate spikes.
With rates at generational highs in 2023–2026, many borrowers who took ARMs expecting to refinance into lower fixed rates are now holding. The rate forecast matters enormously in this decision — consider your personal rate sensitivity before choosing ARM.
