An automatic tire inflator assembly includes an input hose that is fluidly attachable to an air source to receive compressed air from the air source. An output hose is fluidly attachable to an air stem of an inflatable tire. A control unit is fluidly coupled to the input hose to receive the compressed air from the air source. Additionally, the control unit is fluidly coupled to the output hose to inflate the inflatable tire. A gauge is fluidly coupled to the control unit and the gauge is settable to determine the pre-determined threshold pressure. The control unit is turned off when the gauge measures air pressure that exceeds the pre-determined threshold pressure to inflate the inflatable tire to a desired air pressure.