A fixed rate mortgage (FRM) is a mortgage loan where the interest rate on the note remains the same through the term of the loan, as opposed to loans where the interest rate may adjust or "float." Other forms of mortgage loan include interest only mortgage, graduated payment mortgage, variable rate (including adjustable rate mortgages and tracker mortgages) , negative amortization mortgage, and balloon payment mortgage. Please note that each of the loan types above except for a straight adjustable rate mortgage can have a period of the loan for which a fixed rate may apply. A Balloon Payment mortgage, for example, can have a fixed rate for the term of the loan followed by the ending balloon payment.

This payment amount is independent of the additional costs on a home sometimes handled in escrow, such as property taxes and property insurance. Consequently, payments made by the borrower may change over time with the changing escrow amount, but the payments handling the principal and interest on the loan will remain the same.

Fixed rate mortgages are characterized by their interest rate (including compounding frequency, amount of loan, and term of the mortgage). With these three values, the calculation of the monthly payment can then be done.

Unlike adjustable rate mortgages, fixed rate mortgages are not tied to an index. Instead, the interest rate is set (or "fixed") in advance to an advertised rate, usually in increments of 1/4 or 1/8 percent.

Terminology
Fully Indexed Rate—The price of the FRM as calculated by adding Index + Margin = Fully Indexed Rate. This is the interest rate for the life of the loan.
Term—The length of time of the loan. The number of payments is independent of this term, so a 30-year term would have 30 payments for a yearly payment plan, but 360 payments for a common monthly plan.

Popularity
Fixed rate mortgages are the most classic form of loan for home and product purchasing in the United States. The most common terms are 15-year and 30-year mortgages, but shorter terms are available, and 40-year and 50-year mortgages are now available (common in areas with high priced housing, where even a 30-year term leaves the mortgage amount out of reach of the average family).

For example, in Canada the longest term for which a mortgage rate can be fixed is typically no more than ten years, while mortgage maturities are commonly 25 years. In Australia banks are unable to offer fixed rates for terms longer than 15 years due to funding constraints and market collusion at the big end of town.

Pricing
Fixed rate mortgages are usually more expensive than adjustable rate mortgages. Due to the inherent interest rate risk, long-term fixed rate loans will tend to be at a higher interest rate than short-term loans. The difference in interest rates between short and long-term loans is known as the yield curve, which generally slopes upward (longer terms are more expensive). The opposite circumstance is known as an inverted yield curve and is relatively infrequent.

The fact that a fixed rate mortgage has a higher starting interest rate does not indicate that this is a worse form of borrowing compared to the adjustable rate mortgages. If interest rates rise, the ARM cost will be higher while the FRM will remain the same. In effect, the lender has agreed to take the interest rate risk on a fixed rate loan. Some studies [1] have shown that the majority of borrowers with adjustable rate mortgages save money in the long term, but that some borrowers pay more. The price of potentially saving money, in other words, is balanced by the risk of potentially higher costs. In each case, a choice would need to be made based upon the loan term, the current interest rate, and the likelihood that the rate will increase or decrease during the life of the loan.