As it has for the past three quarters, the iPhone will almost certainly represent the single biggest portion of Apple's considerable revenue stream when the company reports its fiscal third quarter earnings two weeks from Tuesday.

    How big?

    That's harder than usual to say. We know that Apple (AAPL) sold at least 1.7 million iPhone 4s in the last three days of the quarter, which ended June 26. What we don't know is the extent to which customers held off buying the old iPhone after Gizmodo leaked specs of the new one on April 19 -- three weeks after the quarter started.

    The estimates of the analysts we've polled are all over the lot, from a low of 7.44 million from J.P. Morgan's Mark Moskowitz to a high of 9.5 million from Piper Jaffray's Gene Munster.

    Even at the low end, that's a 42.8% year-over-year increase from Q3 2009. If Munster is right, iPhone unit sales jumped 82.4% year over year.

    Below: The estimates we've gathered so far. We'll add more as they come in.

Analyst, affiliation   iPhones (millions)  Date of est.

Gene Munster, Piper Jaffray                9.50    6/22/10

Jeff Fidacaro, Susquehanna                 9.44    6/18/10

Robert Paul Leitao, Apple Finance Board    9.40    7/2/10

Andy Zaky, Bullish Cross                   9.30    6/27/10

Jeff Fosberg, Apple Finance Board          9.25    6/3/10

Ashok Kumar, Rodman & Renshaw              9.20    7/1/10

Peter Misek, Canaccord Adams               9.20    4/21/10

Keith Bachman, BMO Capital                 9.20    6/28/10

Daniel Tello, Deagol's AAPL Model          9.04    6/30/10

Shaw Wu, Kauffman Bros.                    9.00    6/29/10

Ralph Schackart, William Blair             8.94    6/28/10

Brian Marshall, Gleacher & Co.             8.75    6/23/10

Yair Reiner, Oppenheimer                   8.60    6/30/10

Doug Reid, Thomas Weisel                   8.54    4/20/10

Richard Gardner, Citigroup                 8.50    6/28/10

Horace Dediu, Asymco                       8.50    6/29/10

Ben Reitzes, Barclay's Capital             8.14    6/22/10

Bill Shope, Credit Suisse                  7.96    4/8/10

Toni Sacconaghi, Bernstein Research        7.88    6/21/10

Scott Craig, Merrill Lynch                 7.80    6/28/10

Turley Muller, Financial Alchemist         7.80    7/4/10

Kathryn Huberty, Morgan Stanley            7.50    7/1/10

Mark Moskowitz, J.P. Morgan                7.44    7/1/10

    . . .