Agro-economic analysis of farm machinery in relation to the specific agro-climatic situation is essential for evolving farm machinery management strategies. Hence such an analysis was done for three different models of four wheel riding type rice transpalnters. Technical data on performance aspects were acquired from studies taken up in the central zone of Kerala state, India. The rainfall data was analyzed with respect to the crop duration of common varieties to obtain the rice transplanting calendar. Curves were plotted depicting the variation of Hourly Operation Costs (HOC) and Unit Area Operation Costs (UAOC) of different machines with respect to annual working hours (AWH). The self-propelled rice transplanters were found to be cost-effective beyond the break even hours and break even areas of annual operation. Fixed cost factor was accounted for the major share of the hourly operating cost of the four wheel type rice transplanters. The probable maximum AWH in the cluster rice fields (padasekharams) of the zone was 300 hours. The variations in the HOC of different machines with AWH revealed that they were always highest for TR1 followed by TR2 and TR3 up to an AWH of 400. Beyond an AWH of 400 hours, even the costliest transplanter TR1 can also be economical, especially for entrepreneurs who can operate at multi-cluster basis. The HOC and UAOC were found minimum for TR1 and TR2, respectively for all AWH values considered.