It's one of Amazon's best-kept secrets. How many computers does it take to keep its Elastic Compute Cloud platform afloat?

And now, a researcher with Accenture thinks he has the answer: 445,000. That's the number that Huan Liu came up with when he did a bit of internet sleuthing. "It's a fairly big site; it's pretty impressive," he says of the entire EC2 operation.

EC2 is Amazon's pay-as-you-go computing service. It's become a popular way to spin up computing power for a corporate skunkworks project or a startup, but it's also the back-end for serious online sites, including Netflix and Dropbox.

Liu's analysis found that Amazon's main cluster of data centers, located in northern Virginia, is truly massive: he guesses that Virginia is home to about 322,000 servers. But he also found that Amazon has a relatively small footprint in other parts of the world. For example, he guesses that there are only 1,600 EC2 servers in Sao Paulo, Brazil. It's "hard to compete with Amazon on scale in the US, but in other regions, the entry barrier is lower. For example, Sao Paulo has only 25 racks of servers," Liu wrote in a blog post discussing his findings.

Liu, a research manager with Accenture Technology Labs, took advantage of the way that Amazon organizes its EC2 domains to come up with his estimate, which strikes us here at Wired as a bit of a lowball guess.

Because Amazon relies heavily on virtual computing – that is, it can host several software-based "virtual" servers on a each computer – figuring out the number of machines in Amazon's data center is a very tough task.

But Liu used a few tricks to link all of Amazon's Domain Name System and IP addresses to actual server racks used by the Internet giant. Then, by guessing that each server rack has 64 machines in it, he came up with his total numbers.

He tells Wired that he's "pretty confident" about the number of racks that Amazon uses. As to whether the company crams 64 or 128 servers in each rack? Well that, nobody knows for sure. "It's an educated guess," he admits.

The estimate also leaves out the servers that are powering Amazon's Virtual Private Cloud, a hosting service for servers that are kept off the Internet, and which couldn't be measured using Liu's techniques.

Nobody knows for sure, but because it buys so many servers, Amazon has probably joined Google, Facebook, and others and come up with custom, energy efficient server designs that are different from what you'd see in most corporate data centers.

Amazon spokeswoman Kay Kinton declined to say anything about Liu's work saying the company doesn't comment on "rumors and speculation."