I use "Know your margin" to calculate it. But as AW10 said, it changes a lot after the transactions. There will be an email "Margin Details XYZ" daily from ICICI before 11AM. This has the latest Margin req for our portfolio.
For example, it was around 80K in "Know your margin", but when it comes to email, it was around 110K.
Off Topic:
Planning to shift to someone else, as brokerage appears to be high with ICICI direct. Together with tax et all, it comes to 110 Rs per slot per trade. Which means, we will end up spending 220 Rs when we close the position. Say we trade with some option around 50 Rs... brokerage is close to 10%
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Same if one has to write covered call. The share buying will cost another ~2% brokerage.
Going through other threads, looks like Reliance money is good. Yet to explore.