This article demonstrates an approach to eliminate phase offsets in time of flight (ToF) measurements of WiFi OFDM signals for precise microwave ranging. Bidirectional channel measurements exploit the characteristic of opposite phase offset signs on the bidirectional link. Orthogonal matching pursuit (OMP) and particle swarm optimization (PSO) algorithms are applied for ranging. Mean, variance and RMS error statistics of the proposed ranging method compare very favorably to perfectly synchronized range measurement methods.