Soil conservation is important from agriculture and environment point of view. The cut slopes or filled up slopes are prone to soil erosion due to rainfall and surface flows. Various types of erosion control blankets, made of synthetic called as geomats or biodegradable fibers, having various thicknesses, tensile properties, and weight, are available for soil erosion control on slopes when exposed to natural weathering agents such as rainfalls and winds. Selection of erosion control blankets from available in the market is usually based on experience, and limited information is available in the literature on how to select the right erosion control materials. Revised Universal Soil Loss Equation (RUSLE) is used to estimate amount of soil loss, which consider climate, soil, topography, soil use, and management. Out of these factors cover management factor called as C factor provides an evaluation of the performance of an erosion control product in reducing soil loss and protecting the slope from the above-mentioned erosive agents compared to the same unprotected slope. The C factor is a performance factor which is estimated through full-scale tests as per ASTM test method. This chapter presents the study of estimation of the C factor associated with a three-dimensional, synthetic geomat through a test campaign conducted according to the relevant standards. Additionally, the chapter presents example of calculation on soil loss for a hypothetical construction site in Nepal.