ARMs offer lower initial rates but adjust over time. Here's exactly how they work, what the caps protect you, when an ARM saves you money, and when to stick with a fixed rate.
ARM Loan — Quick Facts
5/1, 7/1, 10/1
6.38%
−0.44%
5–10 years
2/2/5 typical
Short-term ownership
What Is an Adjustable-Rate Mortgage?
An adjustable-rate mortgage (ARM) is a home loan with an interest rate that changes periodically after an initial fixed-rate period. The rate adjusts based on a financial index — typically the Secured Overnight Financing Rate (SOFR) — plus a lender margin.
ARMs are described with two numbers: the first is the length of the initial fixed period, the second is how often it adjusts after that. A 7/1 ARM has a fixed rate for 7 years, then adjusts once per year afterward. A 5/6 ARM is fixed for 5 years, then adjusts every 6 months.
How ARM Rate Adjustments Work
The Index + Margin Formula
Your ARM rate = Index Rate + Lender Margin. The margin is fixed for the life of the loan (typically 2.5–3.5%). The index fluctuates with market conditions. SOFR (which replaced LIBOR in 2023) is the most common index for new ARMs. When SOFR goes up, your ARM rate goes up. When it falls, your rate falls.
Rate Caps — Your Protection
ARM rate caps limit how much your rate can change. Most ARMs use a 2/2/5 cap structure:
Initial cap (2%): Maximum increase at the first adjustment
Periodic cap (2%): Maximum increase per adjustment period after the first
Lifetime cap (5%): Maximum rate increase over the life of the loan
Example: A 5/1 ARM starting at 6.38% with 2/2/5 caps could never exceed 11.38% (6.38% + 5% lifetime cap), and can rise at most 2% per year during the adjustment period.
Current ARM vs Fixed Rate Comparison
Loan Type
Initial Rate
Vs 30-Yr Fixed
Monthly Savings*
5-Year Savings*
30-Year Fixed
6.82%
—
—
—
5/1 ARM
6.38%
−0.44%
~$89
~$5,340
7/1 ARM
6.45%
−0.37%
~$75
~$4,500
10/1 ARM
6.61%
−0.21%
~$43
~$2,580
*Estimates based on $350,000 loan. Actual savings vary. ARM rate may change after fixed period.
When an ARM Makes Sense
You plan to sell or move within the fixed period (5, 7, or 10 years) — you capture the lower rate without ever facing adjustment
You expect to refinance before the fixed period ends
Rates are unusually high and expected to fall — ARM lets you benefit from drops without refinancing
You need the lower payment to qualify for a larger loan amount
You have a large initial loan — savings are proportionally larger on $500K+ loans
When to Choose a Fixed Rate Instead
You plan to stay in the home long-term (10+ years)
You value payment predictability for budgeting
The spread between ARM and fixed rates is small (<0.25%)
You're near the maximum you can afford — rate risk is too dangerous
Rates are already at historical lows (limited downside for ARM)
Frequently Asked Questions
ARM rate increases are limited by caps. The most common cap structure is 2/2/5: the rate can increase by at most 2% at the first adjustment, 2% at each subsequent adjustment, and never more than 5% total above your starting rate. On a 5/1 ARM at 6.38%, the worst-case rate would be 11.38% — still below historical peaks but significantly higher than today's rates. Always know your cap structure before choosing an ARM.
Most ARM loans originated since 2022 use the Secured Overnight Financing Rate (SOFR) as their index. SOFR replaced LIBOR, which was discontinued in June 2023. Your ARM note will specify the index. Your fully-indexed rate at adjustment = current SOFR + your loan's margin (typically 2.5–3.5%). Historical ARMs still using LIBOR were transitioned to SOFR or another approved replacement index.
Yes — refinancing from an ARM to a fixed-rate mortgage is a common and straightforward transaction. Many borrowers use ARMs strategically, taking the lower initial rate and planning to refinance before the fixed period ends. The main risk is that rates may be higher when you refinance than when you got the ARM. You'll also pay closing costs on the refinance (typically 2-5% of the loan amount).
Disclaimer: Smart Mortgage Guide provides educational content only. We are not a licensed mortgage lender, broker, or financial advisor. Rates, limits, and program details are subject to change. Always consult with a licensed mortgage professional before making financial decisions.