I am assuming that your question is in the reference of jee mains. As you cannot calculate your exact rank because it will depends upon various factors which will vary according to the coming exam in July .
But you can use rank predictor which will give you a range of rank you may get assuming all the factors and based on January exam results.
JEE Main Rank Predictor 2020 - Predict your JEE Main Rank - JEE Main Percentile Calculator
JEE Main Rank Predictor - Know your expected IIT JEE Main 2020 Rank by using Careers360 JEE Main rank predictor tool based on JEE Mains scor ...
Here you need to put your marks and you will get your percentile , category rank and general rank.