hi Omars, what i would do is go to the charts and look back at the last 3 or 4 er's, for GOOG as an example, if they reported on the 20th, i would get the close on the 20th then look at the next days open, calculate the percentage% move, not the dollar value...and do the math myself...to help me predict a possible move for the current er's...
Cree is another example...they report this week as well...a year ago cree was a $45 stock, a ~10% move is $4-5 move on er's,but now its a $25 stock, that same % move is only $2-3...nearly half the dollar value but the same % move...
GOOG historically moves in the area of ~10% on er's..give or take a few dollars...so if GOOg moves ~10%, your looking at a possible $60-70 dollar move...WOW...
but the crazy thing with options is, when the herd is expecting is expecting that huge move...it doesnt come, and everyone gets killed..unless your selling the premium.
its never an absolute...so play carefully