The new estimates from the NPD Group were revealed Monday by Piper Jaffray analyst Gene Munster. NPD's estimates for U.S. sales put Apple up 20 percent year over year in January, 12 percent in February, and 47 percent in March, resulting in an average of 27 percent year over year for the quarter.
Actual Mac sales for the quarter will be known come Wednesday afternoon when Apple reveals its quarterly earnings for the second fiscal quarter of 2011. Apple is scheduled to report its earnings after the market closes, and will hold a conference call at 5 p.m. Eastern to discuss the results.
Munster said a 27 percent year over year increase in Mac sales would represent total sales of between 3.6 million and 3.7 million. The data shows Apple tracking on the high end of Wall Street expectations of about 3.6 million Macs sold in the quarter.
Mac sales growth slowed slightly in February, according to NPD figures, ahead of Apple's MacBook Pro lineup refresh. The new MacBook Pros were released in late February, packing Intel's latest Sandy Bridge processors and the new high-speed Thunderbolt data port.
But Mac sales rebounded strongly in March, the first full month in which the new MacBook Pros were available. Still, Munster noted that Mac revenue is estimated to account for just 21 percent of Apple's revenue in calendar year 2011.
The latest NPD data also showed U.S. iPod sales down 10 percent year over year. International iPod sales are a larger mix than international Mac sales, resulting in a slightly greater margin of error from domestic NPD data.
Drawing assumptions from the NPD data, Munster sees Apple reporting sales of between 9.8 million and 10.3 million iPods for its second quarter of fiscal 2011. That's in line with Wall Street's expectations of 10 million iPods for the three-month frame.