In a good quarter — like fiscal Q2 2012, when Apple sold 35 million iPhones — the device will account for nearly 60% of the company’s total revenue. In a bad quarter — like Q3, when the 26 million units Apple sold accounted for 46% of its revenue — the iPhone will drag the company and its stock price down with it.

Estimating iPhone sales for Q4 2012 — the quarter that ended Sept. 29 — is particularly tricky. For the first 10 weeks, unit sales were depressed by customers holding out for the new phone they kept reading about. For the last two weeks, the company sold iPhone 5s as fast as it could make them.

How fast that was, and how slow sales were before the iPhone 5’s release, is anybody’s guess.

The 60 estimates that have come in so far from our pool of Apple analysts — 30 professionals and  30 independents — were all over the lot. In fact, it was hard to distinguish the consensus among the more conservative pros from the congenitally bullish indies.

The low estimate this quarter, 21 million, was submitted by an independent — Shafiq Shamji of the Braeburn Group. And before he lowered his forecast to 26.5 million on Monday, William Blair’s Anil Doradla was sitting on a Street-and-independent high estimate of 33 million.

The average among both groups is 26.4; the median 27 million.

We’ll find out whose numbers are closest to the mark when Apple reports its earnings after the markets close on Thursday, Oct. 25.

Below: The analysts’ individual estimates, with the pros in blue and the amateurs in green.