Overview
An adjustable-rate mortgage starts with a lower interest rate that adjusts after an initial fixed period (typically 5, 7, or 10 years). A fixed-rate mortgage locks your rate for the entire loan term. The choice comes down to how long you plan to stay in the home and your tolerance for payment uncertainty.
Side-by-Side Comparison
| Feature | Adjustable-Rate (ARM) | Fixed-Rate |
|---|---|---|
| Initial Rate | Lower (typically 0.5-1.5% below fixed) | Higher but locked in |
| Rate After Initial Period | Adjusts annually based on index + margin | Never changes |
| Monthly Payment | Lower initially; may increase later | Same every month for 15 or 30 years |
| Rate Caps | Initial cap (2%), annual cap (2%), lifetime cap (5%) | N/A — rate is fixed |
| Worst-Case Rate | Initial rate + lifetime cap (e.g., 5.5% + 5% = 10.5%) | Same as your locked rate |
| Best For | Staying 3-7 years, or expecting rates to drop | Staying 10+ years, or wanting certainty |
| Risk Level | Higher — payment can increase significantly | None — payment is predictable |
| Common Terms | 5/1, 5/6, 7/1, 7/6, 10/1 ARM | 15-year fixed, 30-year fixed |
Pros & Cons
Adjustable-Rate (ARM)
Advantages
Lower initial rate saves money in the first 5-10 years
If you sell before the adjustment period, you pay less total interest
If rates drop, your payment decreases automatically
Rate caps limit how much your payment can increase
Disadvantages
Payment uncertainty after the fixed period ends
Worst-case scenario could increase your payment by 40-60%
Harder to budget long-term
If rates rise significantly, you may be forced to refinance
Fixed-Rate
Advantages
Complete payment predictability for the life of the loan
No risk of payment increases
Easier to budget and plan long-term
Peace of mind — especially in rising rate environments
Disadvantages
Higher initial rate means higher payments from day one
If rates drop, you must refinance to benefit (with closing costs)
You pay more interest in the early years compared to an ARM
When to Choose Each Option
Choose Adjustable-Rate (ARM) if...
Choose an ARM if you plan to sell or refinance within 5-7 years, you're confident rates will stay flat or decline, or the initial savings are significant enough to offset the risk. Military families, corporate relocators, and people buying starter homes are common ARM candidates.
Choose Fixed-Rate if...
Choose a fixed rate if you plan to stay in the home for 10+ years, you want predictable payments, or you're buying your forever home. Fixed rates are also better when rates are historically low — you lock in the low rate permanently.
The Bottom Line
In most rate environments, a fixed-rate mortgage is the safer choice for long-term homeowners. ARMs make sense when you have a clear exit timeline (selling or refinancing) within the initial fixed period. Use our ARM vs Fixed calculator to model your specific scenario with actual rate caps.
Run the Numbers
Frequently Asked Questions
A 5/1 ARM has a fixed rate for the first 5 years, then adjusts once per year after that. A 5/6 ARM adjusts every 6 months after the fixed period. The first number is the fixed period in years; the second is how often it adjusts.
Most ARMs have three caps: an initial adjustment cap (typically 2%), an annual adjustment cap (2%), and a lifetime cap (5%). So a 5.5% ARM could go as high as 10.5% over the life of the loan.
Yes, and many ARM borrowers plan to refinance before the adjustment period. However, refinancing has closing costs (typically 2-3% of the loan), and there's no guarantee rates will be favorable when you need to refinance.