Analysts scramble to raise their iPhone and iPad estimates by Philip Elmer-DeWitt @FortuneMagazine September 9, 2011, 2:29 PM EDT E-mail Tweet Facebook Google Plus Linkedin Share icons Hasty revisions three weeks before the end of Apple’s last fiscal quarter of the year It happens every three months. As the end of Apple’s AAPL fiscal quarter approaches, the small army of analysts that cover the stock dusts off its spreadsheets, finds them overly conservative and starts issuing revisions. If history is any guide, the numbers will be revised again — upward — when the company reports its Q4 2011 earnings in mid-October. Here are the reports we’ve seen so far this week: Sterne Agee’s Shaw Wu: Sees “remarkable” strength in iPhone 4 sales despite expected release of iPhone 5 in October. Ups iPhone estimate to 18.5 million (from 15.7 million), iPads to 12 million (from 10.4 million) and gross margin to 41% (from 39%). Staying pat on Macs at 4.1 million. Jeffries’ Peter Misek: iPhone sales are “surprisingly strong” he says, but back-to-school demand for Macs was “weaker than expected.” Ups iPhone estimate to 18.9 (from 18.4), lowers Mac to 4.4 million (from 4.9 million). BMO’s Keith Backman: Raises iPhones to 20.4 million (from 19.5 million), Macs to 4.31 (from 4.27 million) and iPads to 11.0 million (from 10.5), adding that he “sees upside tension to 11.5 million units,” whatever that means. Pacific Crest’s Andy Hargreaves: Sees “significant upside” to the numbers in his spreadsheet but doesn’t seem quite ready to change them. Could easily imagine iPhone sales going to 24.05 million (from the 18.7 million in his model) and iPad sales going to 16.5 million (from 11.1 million). For the record, the estimates we’ve seen so far from independent analysts (whose track record is considerably better than Wall Street’s) are higher on iPhones and Macs and lower on iPads. On average, they’re calling for 24.9 million iPhones, 4.85 million Macs and 10.5 million iPads.