I have 100's of sites live and have been working in one area recently that rings true time after time backed up with stats. It goes a little like this on a daily basis .... 15-20 unique visitors 6 of them from Google search will produce 1 call to the advertised number. 40-50 unique visitors 12 of them from Google search will produce 2+ calls to the advertised number. We even got it down to looking at the stats and guessing how many calls had come through. ie. the site had 120 visitors with 20 from Google so guessed 5 calls. Checking the call logs it did have 5 calls. Anyone else had a similar rule of thumb with stats, cash, calls, clicks?