As on date, margin required is around 10% for futures for indexes like Bank Nifty, Nifty, CNX IT and so on.

So below are the calculations for margin required for Bank Nifty to buy one lot in Futures

% Margin = 10.10 %
Lot Size = 25
Bank Nifty Spot = 11820
Margin Required = (25 * 11820) * 10.10 % = Rs 29,848
The margin required will vary as Bank Nifty spot changes every day. So, margin required is approximately 30 K, with Bank Nifty around 12,000.

As Spot value rises, margin required will also rise marginally and vice-versa.

Watch the below video to understand more about Futures trading.

What is Futures Trading (Derivative Trading)