How do I use F&O data (OI) for market direction?

PCR (Put-Call Ratio) = Put OI / Call OI. PCR above 1.2 = bearish sentiment (many put buyers = contrarian bullish). PCR below 0.7 = bullish sentiment (contrarian bearish). Extremes often mark turning points.

Max pain is the strike where option sellers lose least — the market tends to move toward max pain as expiry approaches. Check max pain on websites like optiontradinglevels.com before expiry trading.