Fixed vs Adjustable Rate Mortgage: Which Should You Choose?

When you apply for a mortgage, your lender will offer two basic types of loans: fixed-rate and adjustable-rate (ARM). The choice affects your monthly payment for up to 30 years, so it's worth understanding clearly.

Fixed-Rate Mortgage

Your interest rate is locked for the entire loan term — typically 15 or 30 years.

What you get:

• Same payment every single month
• Complete protection from rate increases
• Easy to budget around

Most common terms:

• 30-year fixed: lower monthly payment, more total interest
• 15-year fixed: higher monthly payment, much less total interest

Example — $350,000 loan:

The 15-year costs $722 more per month but saves nearly $290,000 in interest.

Adjustable-Rate Mortgage (ARM)

Your rate is fixed for an initial period (3, 5, 7, or 10 years), then adjusts annually based on a market index plus a margin.

Written as X/Y: a 5/1 ARM is fixed for 5 years, then adjusts every 1 year.

ARM caps protect you:

• Initial cap: max increase on first adjustment (typically 2%)
• Periodic cap: max increase per year after that (typically 2%)
• Lifetime cap: max increase over the life of the loan (typically 5%)

Example — 5/1 ARM at 6.0%, $350,000 loan:

• Years 1–5: $2,098/month (saves $231/month vs 7% fixed)
• Year 6+: rate can rise to 8% ($2,568/month) or higher

When ARM Beats Fixed

ARMs make sense when:

1. You plan to sell or refinance before the fixed period ends. If you're buying a starter home and plan to move in 5 years, a 5/1 ARM saves money with no rate risk.

2. Rates are high and expected to fall. If current rates are elevated, an ARM lets you benefit from future decreases automatically.

3. You're buying a jumbo loan. ARM/fixed rate spreads are often larger on big loans — savings compound.

4. The rate spread justifies the risk. If the ARM rate is 1.5%+ lower than the fixed rate, the savings in the early years can be substantial.

When Fixed Is the Right Choice

Go fixed when:

• You plan to stay in the home long-term (7+ years)
• Rates are low by historical standards
• You have a tight budget and need payment certainty
• You're risk-averse and want predictability

The Break-Even Calculation

To decide between ARM and fixed, calculate how long it takes for the fixed rate's stability to be worth the higher initial cost.

Example:

• 30-year fixed at 7.0%: $2,329/month
• 5/1 ARM at 6.0%: $2,098/month
• Monthly savings with ARM: $231
• If ARM rate jumps to 8.5% in year 6, extra monthly cost: $388

If you stay past year 8, the fixed rate likely saves money overall. If you sell in year 5, the ARM wins by ~$13,860.

The Bottom Line

• Staying 7+ years? Fixed rate — predictability is worth more than the initial savings
• Moving in under 5 years? ARM — save money with no risk if you sell before the first adjustment
• Rates high right now? ARM gives downside protection if rates fall
• Tight budget? Fixed — never risk a payment shock

Use our Mortgage Calculator to compare exact monthly payments and total costs for any rate scenario.