Optimum seed rate is required for the maximizing the production level of the crops. Use of too high seed rates is not only economically loss but also suppresses the crop growth and finally yields loss. Low seed rate result lower plant population thereby lowers the yield. So, Optimum rate of seed is required. And hence, calculation of seed rate is the need.
Seed rate depends on spacing of crop (row to row and plant to plant), Number of seeds per spot, Thousand grain weight, Germination percentage, Purity percentage.
This seed rate calculator gives the amount of seed required in the given area.