Mortgage Basics

Fixed vs Variable Rate Mortgage: Fixed or ARM? Both Sides on Trial

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Last reviewed: October 2026 · By the MortgageCompass Editorial Team · How we research

A fixed-rate mortgage keeps the same rate for the whole loan. An adjustable-rate mortgage (ARM) starts with a fixed rate for a few years, usually five, seven or ten, then adjusts with the market. In the week ending October 9, 2026, the Mortgage Bankers Association recorded an average 30-year fixed rate of 7.50% and a 5/1 ARM rate of 6.54%, a gap of almost a full point. ARMs made up 10.5% of applications, the highest share in a year. So which should you choose? We put both sides on trial.

Exhibit A: how an ARM actually works

Every ARM is described by a short code, such as “5/6 ARM, 2/1/5 caps”. Most new ARMs follow SOFR, the Secured Overnight Financing Rate, which replaced LIBOR in 2023. After the fixed period, your new rate is the index plus a margin set in your contract, limited by the caps. Tap each number below to decode it, then see the worst case the caps allow.

ARM decoder and worst-case staircase

Tap each number in the loan name to see what it means. The chart shows the highest your rate could climb under the caps, against a 30-year fixed rate.

Assumes the common 2/1/5 caps on a SOFR-based ARM that adjusts every six months after the fixed period. The worst case raises the rate by the maximum allowed at every reset; the other path keeps the starting rate unchanged. Real resets depend on the index and your margin. Default rates are MBA averages for the week ending October 9, 2026 (30-year fixed and 5/1 ARM); longer fixed periods usually start at a slightly higher rate. Not financial advice.

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OPENING ARGUMENT
The case for a fixed rate
  1. Certainty for 30 years. On a $400,000 loan at 7.50%, the payment is about $2,797 a month and never changes.
  2. Rates could rise further. MBA economists expect the Federal Reserve to raise rates again in December and early 2027. With an ARM that resets during a rising period, your payment could jump by more than $1,000 a month at the caps.
  3. You keep a free option. If rates fall, you can usually refinance a fixed loan. If they rise, you are protected. See when refinancing makes sense.
  4. Simpler to budget. No indexes, margins or caps to track.
⚖️
OPENING ARGUMENT
The case for an ARM
  1. A lower payment now. At 6.54%, the same $400,000 loan costs about $2,539 a month, roughly $258 less than the fixed loan.
  2. Real savings if you move on in time. If you sell or refinance before a 5-year fixed period ends, you save about $19,300 in interest compared with a 7.50% fixed loan, with no reset risk at all.
  3. The risk is capped. With 2/1/5 caps, the rate can never rise more than 5 points above the start, and only gradually.
  4. Rates might fall. If they do, the ARM resets lower, or you refinance into a cheaper fixed loan.

Who an ARM can suit, and who should avoid one

An ARM tends to suit borrowers with a clear end date: people expecting a job move, buyers of a starter home they plan to trade up from, or high earners who could easily absorb the worst-case payment and want to keep cash free for other goals. It can also suit borrowers with large loans, where the monthly saving is bigger.

It is usually a poor fit if your budget is already stretched, if this is the home you plan to stay in for decades, or if your income is uncertain. The danger is not the first five years; it is being forced to keep the loan after the reset because you cannot sell or refinance, for example if home values have fallen or your credit has weakened. That is what happened to many ARM borrowers before the 2008 crisis, when loans often had higher caps, teaser rates and weaker checks than today’s.

Cross-examination: questions to ask any lender

  • What is the index and what is the margin? The margin never changes, so a lower margin is worth a lot over time.
  • What are the caps? 2/1/5 is common for six-month ARMs, but some loans allow a 5-point jump at the first reset.
  • Is there a floor? Many ARMs cannot fall below the start rate or the margin, which limits the benefit if rates drop.
  • Which rate do you qualify me at? For ARMs fixed for five years or less, Fannie Mae and Freddie Mac loans are usually assessed at a higher rate, often the start rate plus 2 points, which can reduce how much you can borrow.
  • Any prepayment penalty or conversion option? You want to be free to refinance or sell before the first reset.

The verdict depends on three facts

1. How long you will keep the loan. If you are confident you will sell or refinance within the fixed period, an ARM is hard to beat. Be honest: plans change, and many people stay longer than they expect.

2. Whether you could survive the worst case. Look at the highest payment in the decoder. If that number would put your home at risk, a fixed rate is the safer choice, whatever the forecasts say.

3. That nobody knows where rates are going. Forecasters expect rates to stay above 7% through 2027, but forecasts change quickly. Read our mortgage rate predictions for the latest, and treat them as scenarios rather than promises.

If you choose fixed, also decide between terms: our comparison of 30-year vs 15-year mortgages shows how much the shorter term saves. Check today’s mortgage rates before you lock.

Outside the US

The same choice works differently elsewhere. See our guides to fixed vs tracker mortgages in the UK, fixed vs variable in Canada and fixed vs variable home loans in Australia.

Sources

This guide is for informational purposes only and is not financial advice. ARM terms vary by lender; read your Loan Estimate and the ARM disclosure carefully. Figures are illustrations based on average rates.

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