ARM Calculator
Estimate your initial adjustable-rate mortgage payment, your payment after the first adjustment, and your worst-case payment under the loan's rate caps.
How to Use the ARM Calculator
Enter your loan amount, initial fixed rate, fixed-rate period, and expected rate adjustments to see how your monthly payment could change once the adjustable period begins.
How Adjustable-Rate Mortgages Work
Understanding ARM Labels (5/1, 7/6)
The first number indicates years the rate stays fixed; the second indicates how often it adjusts afterward. A 5/1 ARM adjusts annually after 5 years; a 7/6 ARM adjusts every 6 months after 7 years.
Example: $350,000 Loan With a 5/1 ARM at 5.5%
Initial payment: ~$1,987/month, about $257 less than a 6.75% fixed-rate loan — saving ~$15,400 over 5 years. If the rate adjusts to 7% at year 6, the new payment rises to ~$2,289/month.
Understanding Rate Caps
- Initial adjustment cap (often 2%)
- Periodic adjustment cap (often 1–2%)
- Lifetime cap (often 5%)
Often expressed together as “5/2/5.”
Who ARMs Make Sense For
- Short-term homeownership plans
- Borrowers expecting falling rates
- High-income, short-horizon buyers
Key Risks of an ARM
Rising rates at adjustment can increase payments substantially. Even capped increases can meaningfully strain a budget.
Modeling Multiple Rate Scenarios
Compare flat, moderate-rise, and worst-case (max cap) scenarios against a fixed-rate mortgage before deciding.
Adjustable-Rate Mortgage Payment Before & After Reset
ARMs can change your monthly payment the moment the fixed-rate period ends. Use this calculator to model the “before” and “after” payment for your own loan terms, and review how a reset changes what you owe.
ARM Payment Example (5/1 at 5.5%)
In the example above, a $350,000 5/1 ARM starts at roughly $1,987/month and rises to about $2,289/month if the rate resets to 7%. That ~$300 increase shows why modeling before-and-after payments matters. For the full step-by-step math, see how to calculate an ARM payment.
How Rate Caps Limit Your ARM Payment Increase
Rate caps are the guardrails that keep your payment increase predictable. A typical 5/2/5 ARM can adjust up to 2% at the first reset, 2% per period after that, and no more than 5% above the starting rate over the loan life. Learn how the pieces fit together in how adjustable-rate mortgage payments work.
| ARM Term | Fixed Period | Adjustment Period | Typical Start Rate | After First Reset |
|---|---|---|---|---|
| 3/1 | 3 years | Every 12 months | 6.00% | +2% cap |
| 5/1 | 5 years | Every 12 months | 5.50% | +2% cap |
| 7/1 | 7 years | Every 12 months | 5.75% | +2% cap |
| 10/1 | 10 years | Every 12 months | 6.00% | +2% cap |
ARM Calculator – What the Inputs Mean
Initial Fixed-Rate Period
The number of years your rate stays locked before the first adjustment. Common options are 3, 5, 7, or 10 years (3/1, 5/1, 7/1, 10/1 ARMs).
Index and Margin
After the fixed period, your rate becomes index + margin. The index (typically SOFR) moves with the market; the margin is a fixed premium set by your lender. The sum sets your new rate at each adjustment date.
Periodic and Lifetime Rate Caps
Periodic caps limit how much the rate can change at each reset; the lifetime cap limits the total increase over the loan. Entering these together (for example 2/2/5) gives the most realistic worst-case payment.
ARM vs Fixed-Rate Mortgage — Which Calculator Should You Use?
A fixed-rate mortgage keeps the same payment for the whole term, while an ARM starts lower but can rise after the fixed period. If you plan to stay short-term or expect falling rates, an ARM may save money; if you value payment certainty, a fixed rate is safer. Use this ARM calculator to model the reset, or the mortgage calculator for a fixed-rate comparison.
ARMs and PMI (Private Mortgage Insurance)
If you put down less than 20%, PMI adds a separate monthly cost on top of your ARM payment. That makes the loan-to-value math part of an ARM decision too. Estimate that cost with the PMI calculator, and factor in upfront costs with the closing cost calculator.
Frequently Asked Questions
The rate is fixed for 5 years, then adjusts once per year afterward.
It depends on your loan’s specific caps, typically shown as a series like “5/2/5.”
Yes, in terms of payment predictability, though caps limit the worst case.
Most modern ARMs use SOFR (Secured Overnight Financing Rate).
Yes, many borrowers refinance into a fixed-rate loan before the fixed period ends.
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Disclaimer
This calculator provides estimates for educational purposes only and does not constitute financial, tax, or legal advice. Consult your loan documents and a licensed mortgage professional for precise details.