Amazon, the biggest bookseller in America, is also famously one of the most tight-lipped. Sales rankings are available on the Web site and are updated hourly, but the company doesn’t provide information on how many unit sales it takes to make a title an Amazon bestseller.

Like everyone else, PW couldn’t get sales numbers from Amazon, but by studying the print bestseller list for a two-week period, we were able to determine that a title in Amazon’s top five averages 1,094 print copies sold across all channels, including other retailers, on a typical day. And because the general industry thinking is that Amazon accounts for about 30% of print sales, that means it likely takes around 300 copies per day to reach Amazon’s top five, depending on the day of the week and the time of year.

How was PW able to get this number? We looked at Dark Horse’s The Legend of Zelda: Hyrule Historia, a 300-page collection of historical information, concept art, and chronology of the famous Nintendo video game series. We charted the book’s ranking on Amazon, and during the weeks ended February 24 and March 3, it sold 8,573 copies and 6,128 copies, respectively, at outlets that report to Nielsen BookScan. During that two-week span, Hyrule Historia never fell out of the top five on Amazon’s print ranking. For the week ended March 3, the book sold 6,128 copies at outlets that report to BookScan (which covers about 80% of print units). To account for the units not reported to BookScan, we added 20% to its total of 6,128, which equals 7,660. Based on that total, the book sold, on average, 1,094 copies per day, which means that Amazon sold no more than that number of units on any given day. But because Hyrule Historia is available through other retailers like Barnes & Noble, Target, and even video game chain Gamestop—the book is also sold out on—the realistic estimate is that Amazon sold roughly 30% of the 1,094 copies, or 328 copies per day, on average.

It should be noted that print sales vary week to week on Amazon, and just because a calculated estimate for Hyrule Historia yielded a daily sales number of 328 for the week ended March 3, it doesn’t mean it takes 328 copies sold on any given day to have a top-five Amazon bestseller. For the week ended February 24, for instance, Hyrule Historia sold 8,573 print copies, according to Nielsen BookScan, which means it sold about 1,530 copies per day across all outlets. If we apply our 30% estimate based on how much of print sales are accounted for by Amazon, that means Hyrule Historia sold about 459 copies per day on Amazon to maintain its top-five ranking. During the holiday season and other brisk sales periods, the number to hit the bestseller list is certainly higher, but for large parts of the year it only takes a few hundred copies a day, not a few thousand, to get to the top of Amazon’s daily charts.

'Zelda' Print Sales and Amazon Ranking

Nielsen BookScan Sales Average Amazon Sales Rank
Week Ended Feb. 24, 2013 8,573 2.4
Week Ended March 3, 2013 6,128 3.1

CORRECTION: We incorrectly calculated the total of books sold per week (including outlets not tracked by Amazon) as 7,353; its per day total average as 1,050 and its Amazon estimate as 315 per day.