I know that vega represents the loss/gain that an option experiences with a 1% move in the options IV. So say I have an option position consisting of numerous options, some ITM, some OTM and ATM, basically all over the place. What is the best way to quantify, through a formula or otherwise, the effect that an IV move in one or several of the options in my portfolio, for the same underlying, will have on my MTM? I am working at an Excel spreadsheet for this. I know you can LOOK at a volatility skew graph, but I need a more mathematical approach to this. So if there's any formulas, math or anything else I would really appreciate if someone could tell me about.