Fixed vs Adjustable Rate Mortgage (ARM)
Fixed-rate mortgages give you predictability for the life of the loan. Adjustable-rate (ARM) mortgages start lower but can rise. The right choice depends on how long you'll keep the loan and how much risk you can absorb.
Quick answer
Choose fixed-rate if you'll keep the loan more than 5–7 years or want predictability. Choose an ARM if you plan to move or refinance within the initial fixed period (typically 5, 7, or 10 years) — and only if you can afford the worst-case payment if you don't.
How each loan works
Fixed-rate
Interest rate locked for the entire term (15, 20, or 30 years). Monthly payment never changes (excluding taxes and insurance). Most popular and predictable.
Adjustable-rate (ARM)
Lower starting rate (typically 0.5–1.5% below fixed) for an initial period, then adjusts annually based on a market index (often SOFR + a margin). Common formats: 5/1, 7/1, 10/1 — meaning a 5/7/10-year fixed period, then yearly adjustments.
Real-world cost comparison
$300K loan, current rates: fixed 30-year at 6.5% vs 5/1 ARM at 5.5%:
- Fixed: $1,896/month — same for 30 years.
- ARM start: $1,703/month — saves $193/month for the first 5 years (~$11,580 total).
- ARM after adjustment: payment depends on rates at year 6. If they rise to 8%, payment jumps to ~$2,145.
When an ARM makes sense
- You expect to sell or refinance within the fixed period.
- You're confident your income will rise enough to absorb any future increase.
- Current fixed rates are unusually high and you expect rates to fall.
- Military or career relocations every few years.
ARM risks to understand
- Rate caps: typical caps are 2% per adjustment, 5% lifetime. Worst case can be brutal.
- You can't always refinance: if rates and home values move against you, you may be stuck.
- Payment shock: people who chose ARMs in 2020-2021 are facing significantly higher payments now as their fixed period ends.
Use the calculator
Frequently Asked Questions
Is an ARM safer than it used to be?
Modern ARMs have caps (typically 2/2/5 or 2/1/5) that limit how much the rate can move. They're safer than the unlimited ARMs of pre-2008, but the risk is real.
What's the most common ARM?
5/1 ARMs and 7/1 ARMs are the most popular. The fixed period matches the average homeowner's stay in a home.
Can I refinance my ARM later?
Often yes — but you're betting on being able to qualify and on rates being favorable. No guarantee.
Are interest-only ARMs ever a good idea?
Rarely for primary residences. They were a major contributor to the 2008 housing crisis. Most experts recommend avoiding them.
Related Guides
More reading from the Mortgage & Affordability library.
FHA vs Conventional Loan: Which Is Right for You?
Compare FHA and conventional mortgages — down payment, credit requirements, mortgage insurance, and total cost — to choose the right loan.
Read guideMortgage & AffordabilityHow Mortgage Amortization Works
Understand exactly how each mortgage payment is split between interest and principal — and how that ratio shifts dramatically over time.
Read guideMortgage & AffordabilityThe 28/36 Rule Explained
What the 28/36 rule means, how lenders use it, and how to apply it to your own home buying decision — with examples by income.
Read guideRelated Calculators
Put the numbers to work with our free calculators.
Mortgage Calculator
Estimate your monthly mortgage payment in seconds.
Affordability Calculator
See the home price you can comfortably afford.