What are the ways to calculate a how much a website should be bought for (website worth)?

Our tool at http://Flippa.com/valuation is based on $100,00,000 in actual auction data on Flippa but is not reliable for extremely high-end sites (i.e. over $500K+) where we don't have enough sales data. For further reading & thoughts on the subject, see: http://blog.flippa.com/forget-everything-you-know-about-website-valuations/ http://blog.flippa.com/guest-post-5-ways-to-value-a-website/ http://blog.flippa.com/10-factors-that-can-skyrocket-or-tank-the-value-of-a-website/

You really need to delve into the books of a company to get a better understanding of their costs, gross, margins, risk factors, reputation, assets, etc. And, you need to spend time interviewing the owners to find out as much about the things that books don't tell you or that the books are not clear about.  Basically, perrforming "due diligence."  You cannot get the real full story from afar.

Try these links. http://goo.gl/WRMM5. Obviously they're not going to be exact and might not even be close since they don't know very much about the website other than some really basic info, like page rank, etc, but it might give you a general idea. There are many factors involved in appraisal, including website age, niche type, page rank, daily revenues, amount of daily/monthly traffic, etc. If you're serious you can always try to find a website broker or a company that specializes in purchasing websites ( http://www.bizbroker24.com/ ). I hope it helps. Good luck.