Adjustable Rate Mortgage Calculator
This calculator helps you to determine what your adjustable mortgage payments will be.
How the adjustable rate mortgage calculator works
It amortizes the loan at the low initial rate to find your starting payment, computes the balance remaining when the fixed period ends, then re-amortizes that balance at the estimated adjusted rate over the remaining term to show the reset payment.
Worked example: with loan amount of $320,000, loan term (years) of 30 and initial rate of 5.50%, the adjustable rate mortgage (arm) calculator shows initial monthly payment of $1,816.92.
- Initial payment
- $1,816.92
- Payment after reset
- $2,186.48
- Balance at adjustment
- $295,874
- Rate change
- 5.50% → 7.50%
The formula
Initial payment = P × r ÷ (1 − (1 + r)⁻ⁿ). After the fixed period, the remaining balance is re-amortized at the adjusted rate over the remaining months.
Results are estimates for educational purposes and are not financial advice. Confirm exact figures with your lender, plan administrator or advisor.
Questions about the adjustable rate mortgage calculator
What is an adjustable rate mortgage?
A loan with a low fixed rate for an initial period (often 5, 7 or 10 years) that then adjusts periodically based on a market index. Payments can rise or fall after the reset.
Is an ARM a good idea?
It can be if you will move or refinance before the reset, or expect rates to fall. The risk is a higher payment you must be able to afford when the rate adjusts.
How high can my ARM payment go?
Rate caps limit each adjustment and the lifetime increase. Always check the periodic and lifetime caps — they define your worst-case payment, which this estimate approximates.
Is the Adjustable Rate Mortgage Calculator free to use?
Yes. Every calculator on FinCalculators is completely free, with no sign-up, login or paywall. You can run as many scenarios as you like.