These are the top three best of the interior design online software that might come in handy. First is My Deco 3d Room Planner. It has pre loaded plans that you can use to experiment. You can also upload your own plans then customize them further using this software. It has the ability t show you the 3D image and blueprint image at the same time. It has a simple user interface that makes it favorite of many people.
Second best online interior design software is the Homestyler created by Autodesk. It is basically user friendly software without the need of such formal training or course to master it. It offers a simple drag and drop interface to deal with every piece of design. This interior design online also offers the Pro version that will be very suitable for expert users. There are many furniture items available as well to really personalize your design using this software.
Last one is the IKEA Home Planner that you can use to design your interior using the catalog of items supported fully by IKEA. You can try to place IKEA products in your design and see whether they look good or not. It is free interior design online software with easy to use user interface.