This handy little piece of software seamlessly integrates into Hammer and allows on-the-fly conversion of Source Engine units into metric or imperial units. It turns Hammer's rarely-used left-side of the status bar into a non-obtrusive real-time converter, showing the dimensions of an object in chosen units as you work on it, be it creating or resizing it in one of the 2D views. It proves incredibly useful when creating life-sized environments. The conversion ratios come from data available on the VDC (Valve Developer Community) wiki. As is explained, architecture (as well as props), human character models and 3D Skyboxes all work on different scales. Using this tool, you can easily switch between world-scale, human-scale and skybox-scale all within Hammer.
I wrote this program using AutoHotKey, a script language based on AutoIt. The source (.ahk file) is included in the zip file. You can modify, compile and redistribute the code any way you want, without even necessarily having to share your modified source if you don't want to (although that wouldn't hurt anyone). Just make sure you give credit :)
This program works without known issues and is able to handle any number of instances of Hammer running concurrently.
Please note that a desktop resolution of 1280x1024 or higher is required. Lower resolutions unfortunately can't display the conversion information in its entirety.
Program created by Naoki Lambelet - naoki.ch