The dimension analysis is solve to more difficult problem, simplify to difficult equation, reduce the many parameters in equations and search on the parameters more effect of equations. Increase the evaporation from soils and surfaces water with increase transpiration from plants because of raising in temperatures and reducing in humidity are problems of the times which effect on reducing of water. To solve the problems must research on formulas which give actual effects to control on the water reduction by evapotranspiration. In this study will search on methods to solve the crop coefficient (Kc) and evapotranspiration (ET) with multi variables. In this research will be driven equations by statistic of excel program of reference evapotranspiration (ETo) and crop evapotranspiration (ETc) with respect to. From equations and drawings were obtained on maximum value of correlation coefficient(R2). In addition to use the dimension analysis to multi variables (time, number hours of days, relative humidity, change of moisture content, hydraulic conductivity, root depth and temperature) with maximum value of (R2). Researching on equations and methods help to obtain results instead of going back to tables and curves as well reducing field tests that are tired. From equations of ETo and ETc are obtained on R2=0.999 and R2=0.997, respectively from data. From statistic and dimension analysis equations are obtained on result very close with field data with little difference 10% and 4.28%, respectively.