Can I use implied vol or implied move ( .85 * ATM straddle ) to calculate long/short ratios for stocks, ETFs, sector ETFs, etc.? Maybe with beta? I'm currently just using change in price estimates, or % change in price to balance the spreads. I want to day trade S&P sector ETF spreads, stock basket spreads, and other kinds of price differentials. It's a hassle to price all the spreads. It's very easy to look up a hedge ratio for rate and index futures. For other listed securities, not so much. Just like you can use the CME intermarket ratios for futures, I need fast ratios for pairs and baskets, etc. Got a website or quick and dirty formulas? Rule of thumb?