Informações recebidas no TripAdvisor aqui
A person coming into India from abroad can bring with him/her foreign exchange without any limit provided if foreign currency notes, or travellers cheques exceed US$ 10,000/- or its equivalent and/or the value of foreign currency exceeds US$ 5,000/- or its equivalent, it should be declared to the Customs Authorities at the Airport in the Currency Declaration Form (CDF), on arrival in India.Just one need to make a declaration on custom /immigration form if it exceeds limit.The declaration limit is per person basis .
In addition, one can carry up to Rs 5000 in Indian Rupees while traveling to or from countries other than Nepal and Bhutan. There is no limit for these two countries.
There is no fee or charge for carrying foreign currency into India while coming from abroad and neither a stipulation to convert the foreign currency at airport. You can convert as and when and where you need to .