ARM vs Fixed Calculator

Compare an adjustable-rate mortgage to a fixed-rate loan over time.

Loan amount

Term (yrs)

ARM intro (yrs)

Fixed %

ARM intro %

ARM after %

Fixed / mo

ARM intro / mo

ARM payment after reset

Total cost — Fixed

Total cost — ARM

How to Use

1. Enter the loan amount and term.
2. Set the fixed rate, and the ARM's intro rate plus its likely adjusted rate.
3. Choose the ARM intro period (e.g., 5/1).
4. Compare monthly payments and total cost over the intro period and full term.

Calculation Method

Both loans use the standard mortgage formula. For the ARM, the intro period is amortized at the intro rate; after that, the remaining balance is re-amortized at the adjusted rate for the remaining term. Totals sum all scheduled payments.

Data sources: Standard amortization formula applied to both loan structures.

Examples

$320,000, 5/1 ARM 5.5%→7.5% vs 6.5% fixed

The ARM saves money for the first 5 years but can cost more over 30 years if it adjusts up.

Frequently Asked Questions

The rate is fixed for the first 5 years, then adjusts once per year afterward based on an index.

If you expect to move or refinance before the fixed period ends, the lower intro rate can save money.

After the intro period, your rate and payment can rise significantly if market rates increase.

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Mortgage Information Disclaimer

The mortgage calculations on this site are estimates based on the information you provide. Actual mortgage terms, interest rates, and payments will vary based on your credit score and history, debt-to-income ratio, property type and location, loan program, lender-specific requirements, and market conditions.

SmartMortgageCalcs does not provide mortgage, financial, or legal advice. We are not a mortgage lender or broker. We strongly recommend consulting with multiple licensed mortgage lenders, working with a qualified real estate agent, reviewing all documents carefully before signing, and seeking advice from a financial advisor. Our estimates do not constitute a loan offer or commitment — final loan terms are determined by the lender. Interest rates and fees shown are illustrative only.

Last updated: May 19, 2026