How to calculate potential earnings for website

Hi all
I am trying to get investor for big project but I am having trouble presenting potential earnings for my website.
Is there a way to do it, at least approximately?
What all we should take into consideration?
Eeg. if I have website about shopping niche with paying clients who publish content and earnings from banners.
How can i estimate earnings per, for example 1000 visitors?

See original post by clash