Computing the growth of any entity over a time period is important for understanding the past behavior and for future planning. Linear growth rate and compound growth rate are the frequently used methods for calculating the growth rate. The study was carried out using different growth models viz., linear, logarithmic, inverse, quadratic, cubic, compound, S- curve, growth, power and exponential models to project the area, production and productivity of onion crops in Tamil Nadu for the study period 1990-91 to 2016-17. For onion crop the study revealed that through all models exhibited significant; cubic, growth and quadratic model were found to be best for area, production and productivity of onion respectively. Because of highest R2, adjusted R2 and least MAPE values. Decreasing trend with respect to onion area and increasing future projection trend with respect to onion production and productivity. Temporal variation within cluster for productivity of onion was 0 to 1 per cent.