Microsoft has sold roughly over 1 million Surface RT and 400,000 Surface Pro units since launch, according to Dina Bass of Bloomberg, bringing the total number of Surface units to roughly 1.5 million. 

Unlike Apple, Microsoft isn't keen on giving sales numbers for its newly launched hardware line-up. The numbers provided by Bloomberg, citing sources, give us the first real indication of how the Surface platform is performing. It's not clear where these numbers came from specifically, so take it with a grain of salt.

The Surface RT first came to market in October 2012. To compare, Apple sold 22.9 million iPads during the fourth quarter of 2012. They're different months, but should give an idea of performance. 

The Surface Pro is newer on the scene, having seen a limited US launch in early February, and launching in the UK in the near future. The Surface Pro sold out on its opening weekend, more than likely because of limited stock. It's worth noting that a few Microsoft stores saw Apple launch-like lines. 

It looks like the Surface Pro is off to a better start than the Surface RT. We've reached out to Microsoft in the hope of learning more.