To calculate INR equivalence of USD you should know the current conversion ratio. Now here is an example :- 500 USD in INR.
Suppose the present USD INR conversion ratio is 1:50 (1 USD = 50 INR).
To transform 500 USD in INR, you have to multiply 500 x 50. So the amount will be 25,000 Indian Rupees.
Hope you understood how to convert US Dollars to Indian Rupee.