This paper introduces an optimum reference detector design for uncooled resistive microbolometer focal plane arrays (FPAs). Reference detectors are mainly used for canceling the bias heating and for decreasing the ambient temperature dependence of the system. The proposed method in this paper determines an optimum thermal conductance value for the reference detector such that it is almost infrared blind, but still has the same bias heating characteristics as the active microbolometer detector. Infrared blindness of the reference detector is further increased by covering the top of the detector with an infrared reflective material. An optimum number of reference detectors are determined such that the over-heating of the reference detectors is prevented. Simulation results show that, with the use of the proposed method, it is possible to compensate the resistance change due to bias heating by 87% for the specific case where the detector has 60 kΩ resistance biased at 2 V, 10 ms thermal time constant, and 0.5×10-7 W/K thermal conductance.