- APR
- The annual percentage rate: the yearly cost of the loan including certain lender fees, expressed as a single rate. For an ARM, it also depends on an assumed future rate. This calculator assumes the adjusted rate holds for the rest of the term, so the real APR will differ if the rate moves again.
- Adjustable-rate mortgage (ARM)
- A mortgage whose rate is fixed for an initial period and then resets at set intervals, based on a market index plus a margin, within rate caps. A 5/1 ARM is fixed for five years and then adjusts once a year. This calculator models a single adjustment to one estimated rate.
- Initial rate
- The introductory interest rate during the ARM’s fixed period, often lower than a comparable fixed-rate loan. It sets the initial payment. Because the APR blends this rate with the adjusted rate and fees, a low initial rate on a short fixed period can still produce a relatively high APR.
- Fixed period
- The number of years the initial rate is locked before the first adjustment, such as 5 on a 5/1 ARM or 7 on a 7/1. The longer the fixed period, the more of the loan’s interest is charged at the initial rate, and the less the assumed adjusted rate affects the APR.
- Adjusted rate
- The estimated rate after the fixed period ends. In practice it equals the index value at reset plus the margin, limited by the caps, and it can change again at each later adjustment. This calculator holds your estimate constant for the rest of the term when computing the payment and APR.
- Discount points
- Upfront fees paid to the lender to lower the interest rate. One point equals 1% of the loan amount, so one point on a $300,000 loan costs $3,000. Points are included in the Lender Fees & Points input here, and they raise the APR above the note rate because they reduce the amount financed.
- Amount financed
- The loan amount minus prepaid finance charges such as origination fees and points. You repay the full loan amount but effectively receive only this net figure. APR is the rate at which the scheduled payments repay the amount financed, which is why fees push it above the note rate.
- Rate caps
- Limits on how much an ARM rate can change: at the first adjustment, at each later adjustment, and over the life of the loan. They are set in the loan documents and vary by lender and product. This calculator does not apply caps, so enter an adjusted rate that the caps would actually allow.
- Index and margin
- The two parts of an ARM’s adjusted rate. The index is a published market rate that moves over time; the margin is a fixed percentage the lender adds, set when the loan is made. Once the fixed period ends, the new rate is index plus margin, subject to the caps.
