In this study, we determine cost minimizing machinery selections for rice farming by solving mixed integer programs with various acreage constraints. Results indicate that small farms can lower costs by hiring customized machinery operations including plowing, rotary tillage, transplanting, harvesting. Farms equipped with large size farm machines can earn extra income and save fixed costs by providing customized services for neighboring small farms. The optimal size of a single paddy farm is found to be 45 to 50 hectares. Policy support is needed for improving machine performance that can lead to increased optimal acreage as well as decreased cost.