3DMark will benchmark your pc for free and provide cross-platform comparisons

[riso]

Publisher's Description.
From Futuremark:
The new 3DMark (2013) includes everything you need to benchmark your hardware.

With three all new tests you can bench everything from smartphones and tablets, to notebooks and home PCs, to the latest high-end, multi-GPU gaming desktops. And it's not just for Windows. With 3DMark you can compare your scores with Android and iOS devices too. It's the most powerful and flexible benchmark we've ever created.

The latest version of the world's most popular benchmark is simply called 3DMark to reflect its all-round versatility. Not only is this 3DMark the first in the series to offer cross-platform comparisons, it is also the first to test different Direct3D feature levels within one application.
Download
Source: CNET