Everyone loves to get something for free, but if that something doesn't do what it's supposed to... it's still overpriced. On the other hand, if it's free and it's just what you're looking for, it's like finding money in the street. If you're looking for basic CAD software packages and do not need highly technical functionality, you likely will find all you need, and maybe more, in one of these four quality packages that you can download for free.
AutoCAD Student Version
AutoCAD, the heavy hitter of the CAD industry, offers a free, fully functional version for download to students and faculty. The only limitation on the software is a watermark on any plots you generate, designating that the file was created with a non-professional version.
Not only does Autodesk offer its base AutoCAD package free, but it also offers free licenses for almost its entire suite of AEC vertical packages, such as Civil 3D AutoCAD Architecture, and AutoCAD Electrical.
If you're looking to learn CAD or just do some personal design work, this is absolutely the way to go.
Trimble SketchUp
SketchUp was originally developed by Google and was one of the greatest free CAD packages ever put on the market. In 2012, Google sold the product to Trimble. Trimble has enhanced it and developed it further and now offers a slew of related products. Its SketchUp's free web-based version has plenty of power, but if you need additional functionality, you can buy SketchUp Pro — and pay a hefty price tag.
The interface makes it easy to get up to speed on the basics. Even if you've never done any CAD work or 3D modeling before, you can pull together some really nice presentations in minutes.
Of course, if you're looking to put out detailed designs with accurate sizing and tolerances, you'll need to spend some time learning the ins and outs of the program. The SketchUp website offers a really impressive array of video and self-paced training options to help you along the way.
The company no longer develops Sketchup Make, its free desktop software, but you can download it from Trimble's archives.
FreeCAD
FreeCAD is a serious Open Source offering that supports parametric 3D modeling, which means you can modify your design by going back into your model history and changing its parameters. The target market is mostly mechanical engineers and product design, but it's got a lot of functionality and power that anyone would find attractive.
Like many open-source products, it has a loyal base of developers and can compete with some of the commercial heavy hitters because of its ability to create real 3D solids, support for meshes, 2D drafting and lots of other features. Further, it's customizable and is available on multiple platforms, including Windows, Mac, and several Linux distributions, like Ubuntu, and Fedora.
LibreCAD
Another Open Source offering, LibreCAD is a high-quality, 2D-CAD modeling platform. LibreCAD grew out of QCAD, and, like FreeCAD, has a large, loyal following of designers and customers.
It includes lots of powerful features that include snap-to-grid for drawing, layers, and measurements. Its user interface and concepts are similar to AutoCAD, so if you have experience with that tool, this should be easy to get familiar with.