Weighing lysimeters are used to measure crop evapotranspiration (ETC) during the growing season. A ratio of crop evapotranspiration (ETC) to reference evapotranspiration (ETO) determines a crop coefficient (KC) value, which is related to specific crop growth development to improve the KC values. Determination of KC is important to estimating crop irrigation requirements using meteorological data from weather stations. The objective of the research was conducted to determine growth-stage-specific KC and comparison to existing FAO KC values and water use for maize (Zea Mays) at Water Technology Center Research field in Indian Agricultural Research Institute (IARI), New Delhi, India in 2010. Three lysimeters, weighing about 3.5 Mg, consisted of undisturbed 1.5 m deep soil. Accumulated seasonal crop water use was about 411 mm, also the KC values determined during the growing seasons varied from 0.53 to 1.21 for maize. The calculated and measured evapotranspiration were compared to assess the performance of the crop coefficient (KC). The NSE, RSR, RMSE and R2 values indicated that the KC performed ‘Good’ in estimating the seasonal evapotranspiration of maize seasons. However, with respect to different growth stages, agreement between the calculated and measured values varied from ‘Satisfactory’ to ‘Very Good’. The KC values for initial, Develop, mild and late stage were: (0.40 to 0.60), (0.70 to 0.80), (1.1 to 1.21) and (0.50 to 0.65), respectively. Some of the KC values corresponded and some did not correspond to those from FAO-56 values, especial during initial growth stage. So, determination of KC for crops in different regions and climates is important to improve irrigation water management.