Adjustable rate mortgage (ARM)This calculator shows a fully amortizing ARM which is the most common type of ARM. The monthly payment is calculated to payoff the entire mortgage balance at the end of the term. The term is typically 30 years. After any fixed interest rate period has passed, the interest rate and payment adjusts at the frequency specified. A Fully Amortizing ARM will also have a maximum rate that it will not exceed. Below is a list of the most common types of Fully Amortizing ARMs.