Microsoft's free Web version of Office may have surpassed its competitor Google Docs with users.

Nearly 50 million people use Office Web Apps monthly, Microsoft said Wednesday morning. Microsoft started offering free Web versions of Office for the first time last year.

The last time Google gave an estimated numbers on people using Google Docs and the pay version Apps, the company said it had 25 million active users. On Wednesday, Google vaguely said it had "tens of millions" of users.

Office 2010 started selling a year ago and Microsoft posted a blog post Wednesday about how the software is doing in the market. As we reported earlier in our interview with Microsoft Business division president Kurt DelBene, Office 2010 is selling five times faster than Office 2007.

On Wednesday, the Microsoft store at Bellevue Square is giving away a free copy of Office 2010 to the first 50 customers. All Microsoft retail stores in the country are doing the same promotion Wednesday.

Microsoft is expected to start selling a cloud version of Office called Office 365 on June 28.

Update 6/16/11 at 10:22 a.m.:

Google gave gave more details Thursday about how Google Apps and Docs are performing.

Google Docs, the free Web apps that compete with Office Web Apps, has "tens of millions" of users.

Google Apps, the pay version of Google Docs for businesses, has 30 million customers, the company said Thursday. Google Apps competes with Microsoft's Business Productivity Online Services (BPOS), which will be rebranded as Office 365 at the end of June.

It's still a possibility that Office Web Apps may have surpassed Google Docs with users.