I want to buy stock in future lot nrml (dec) value 5lakh how much cash required for this trade

If you want to know what is the margin for stock future please go through the bellow link as it varies for each script.

https://zerodha.com/margin-calculator/Futures/

This post explains how to calculate the amount required to buy or sell any F&O.

The amount requires varies between stock and index and as well as between one stock to another stock. So you need to calculate yourselves and see.