There are plenty video converters online and available to download. Of course, a paid program will offer more advanced features than a free one, but there are free ones that will convert files to another formats as well .
I personally use Handbrake and FreeMake Video Converter. The first one is free while the second one bundles 3rd party installations, but they can be removed while installing. However, HandBrake focuses only on transcoding while FreeMake is an all around program. They're not the best ones, but will do most of the jobs (eg. downloading videos from YouTube, Vimeo, converting, etc).
I have tested he Syncios, and it's not entirely free, as it has a Registration button to acquire the Pro version. The standard version (aka Free) will do most of the jobs which is good for the standard user.
To enjoy Syncios in its full mode, you need to buy it as shown in the image below: