Amazon's algorithm for sales ranking is complicated and some recent attempts to extrapolate the data have yielded some basic guidelines.
Discusses approximate sales from sales ranking. Here he mentions that a book needs to sell a copy a year on Amazon, through Amazon direct or a marketplace merchant, to have an approximate sales rank of 2,000,000. Less than a sale a year results in a larger number, or a worse ranking. A book without a sales ranking has yet to make a sale.
Similarly, Brent Sampson yields this list:
2,000,000+ Perhaps a single inventory/consignment copy has been ordered
1,000,000+ Current trends indicate total sales will most likely be under 40
100,000+ Current trends indicate total sales will most likely be under 200
10,000+ Estimate between 1 - 10 copies being sold per week.
1,000+ Estimate between 10 - 100 copies being sold per week.
100+ Estimate between 100 - 200 copies being sold per week.
10+ Estimate between 200 - 1000 copies being sold per week.
Under 10 Estimate over 1,000 copies per week
But again, being listed does not guarantee sales, and potential sales don't pay your bills.
Apr 9, 2009
Amazon Sales Rankings
Dave Fortier provided some links to explain the Mystery That Is Amazon Sales Ranking.