Adsense

As Adsense publishers are mainly paid from the funds submitted by Adwords advertisers, your earnings depend on the type of ads displayed at your website. 

To forecast adsense earnings, the cost per click (CPC) of the ad unit, the click through rate (CTR) and the page views are used.

The formula for earnings calculation is:

CPC x CTR x PageViews

For the sake of argument, your website has 1,000 visitors a day and each visitor views 2 pages, there will be 2,000 page views per day. 

Now if your average CPC is $0.50 and the CTR is 2% (2 ad clicks per 100 page views), your earnings will be 0.5*0.02*2000 = $20 per day.