Abstract: Numerical simulations were conducted for the laminar flow of water through 22 microchannels with staggered square short micropinfin arrays with various geometry parameters in the Reynolds number range of 5 to 400. The effects of height and pitch of pinfin arrays on laminar flow friction factor were investigated. An empirical correlation was developed as a function of porosity and tortuosity, Reynolds number, and aspect ratio. It is found that this correlation can predict the friction factor in microchannels with micropinfin accurately. It is expected that this novel form of correlation equations can be extended for micro pinfin arrays with complex and irregular geometries and porous media with complex microstructures.