Fair Market Rents (FMRs) are calculated to determine how much a landlord is able to accept for rent of a unit to a Section 8 voucher recipient. FMRs are gross rental rates and dictate the maximum rental rate to be agreed upon in a lease document. The calculation of FMRs is based on a standard quality rent from the five year American Community Survey, as well as a recent mover adjustment, which is the relationship between the standard quality for five years and the one year recent mover rents. FMRs also include a CPI adjustment and a trend factor adjustment. The trend factor adjustment is how HUD expects rental rates to grow.

FMRs include all major utilities (heat, electricity, etc.), but does not include telephone, cable, satellite television, or internet service. Utilities are included in FMRs whether the obligation of payment is under the tenant or the landlord.

In larger metropolitan areas, the calculation of FMRs has been updated to a new system that examines FMRs by ZIP code, as opposed to in total. It's called the Small Area Fair Market Rents Program (SAFMRP) and it was officially implemented by HUD in January 2017, and made mandatory in October 2019.

HUD stated that this program is aimed to allow voucher recipients to move into higher opportunity areas by adjusting the voucher amount, thus reducing the concentration of voucher recipients into lower-income residential districts.