Accurate estimation of evapotranspiration in a paddy field is crucial for efficient water management. Researchers in Japan determined crop and soil evaporation coefficients to estimate evapotranspiration. They used pan evaporation and detailed meteorological data to calculate evapotranspiration. The crop coefficient varied throughout the growing stages of the rice paddy field, while soil evaporation remained low and constant after the leaf area index reached 3. The proposed coefficients accurately estimated evapotranspiration and evaporation. A simple model using leaf area index was developed to estimate soil water evaporation.