There is a relation between Aug. copper and Sept copper, based on carry charges, storage costs, etc. how do I figure out that formula? Thanks a lot!
It's much complex than you think. There is no formula for getting that spread. All things are considered between two contracts, including: interest rate, supply/demand, storage charge, ... etc. Also the contango or backwardation between months. My suggestion is to trade the month that has the highest liquidity and to forget about the spread issue.