ARM Mortgage Calculator

An adjustable-rate mortgage is a home loan where the interest rate changes periodically after an initial fixed-rate period. For example, a 5/1 ARM has a fixed rate for the first 5 years, then adjusts every 1 year after that. ARMs typically start with a lower rate than fixed-rate mortgages, which can mean lower initial payments.

An ARM can be a good choice if you plan to sell or refinance before the initial fixed period ends, or if you expect interest rates to fall. A fixed-rate mortgage offers predictable payments for the life of the loan and may be better if you plan to stay long-term or want protection from rising rates. Your financial situation and risk tolerance are key factors.

During the initial fixed period, your payment is calculated like a standard fixed-rate mortgage using the starting rate and full loan term. After the fixed period, the rate adjusts based on a market index (such as SOFR) plus a margin set by your lender. Rate caps limit how much the rate can increase at each adjustment and over the life of the loan.

ARM rate increases are governed by three caps: the first adjustment cap (limits the rate change at the first reset), the subsequent adjustment cap (limits changes at each later reset), and the lifetime cap (the maximum total rate increase over the loan's life). A common structure is 2/2/5 — meaning 2% at first adjustment, 2% per subsequent adjustment, and 5% maximum total increase.

The most popular hybrid ARM structures are 3/1, 5/1, 7/1, and 10/1. The first number is the initial fixed-rate period in years, and the second is how often the rate adjusts after that (usually every 1 year). A 5/1 ARM is among the most common, offering 5 years of stability before annual resets begin.

A standard (or traditional) ARM adjusts from the very beginning, often after just 6 or 12 months. A hybrid ARM combines a fixed-rate period (typically 3–10 years) followed by periodic adjustments. Most modern ARM loans are hybrid ARMs, which offer an initial period of payment stability that many borrowers prefer.

ARM rates are tied to a financial index such as the Secured Overnight Financing Rate (SOFR), which replaced the older LIBOR benchmark. Your lender adds a fixed margin to the current index rate to determine your new rate at each adjustment. The SOFR index reflects short-term borrowing costs and changes with broader market conditions.

ARMs tend to work well for borrowers who expect to move or refinance within a few years, those who want lower initial payments to qualify for a larger loan, or buyers who anticipate their income will rise substantially. They carry more risk for borrowers who plan to stay in their home long-term, since payments can increase significantly after the fixed period ends.