A novel method to reduce the fixed error of the FMCW radar measuring the distance to single target is proposed and has been studied both theoretically and experimentally. This method determines the distance from the weighted sum of the zero crossings of the beat signal in the FMCW radar, and is named the weighted counting method (WCM). The WCM is a generalized concept of the double modulation method (DMM) which was formerly proposed by the authors; the DMM is equivalent to the WCM employing the triangular weighting function. Applying the Poisson's formula, it has been shown that the fixed error is effectively reduced by employing the weighting function of which the Fourier transform has a low side-lobe level. The weighted counting errors for typical weighting functions: the rectangular function and its convolutions, cosn functions, (1/4-t2)n functions and finite trigonometric serieses have been estimated. Many weightning functions show more accurate results than the DMM does. The effects of the non-linear frequency modulation on the accuracy of the WCM was studied by numerical simulation. It has been clarified that the WCM is scarcely affected by non-linear frequency modulation. The weighted counting FMCW radar employing cos4 weighting function has been realized by a simple analog signal processing circuit, and the experimental measurements were carried out. The position of aluminum plate located at approximately 1m distance was determined with the accuracy of 1.5mm. Based on the experimental results, it has been shown that the accuracy of the FMCW radar is restricted by the mismatches in the microwave circuit, when the fixed error is sufficiently reduced.