For better benefits and yields, a good estimation of grapes quantity in vineyard is necessary. In this paper, three-dimensional (3D) imagery technique using conventional 24GHz Frequency-Modulated Continuous-Wave (FMCW) Radar is applied for detecting and remotely estimating the intra-parcel quantity of grapes. An estimation is possible even in presence of natural or artificial clutters such as leaves, wood or irrigation hoses. The microwave sensing is performed from the radar beam scanning of a vineyard and an estimator is defined to derive the quantity of grapes in grapevines from radar echoes distribution in the interrogated 3D scene. An algorithm based on contour detection is applied to the 3D radar image and a new parameter, called the spread factor, is defined for classifying the echo levels of grapes. The quantity of grapes is finally deduced from an appropriate estimator. This remote sensing approach brings a new and flexible solution for precision viticulture by estimating the grape quantity even for grapes hidden by leaves.