There are two quick ways of generating a magnet link from the .torrent file, using uTorrent(the popular Bittorrent client) and Magnetizer(a tool that nobody has heard about before).
Open .torrent file with uTorrent, right-click the torrent, and select Copy Magnet URL from the context menu.
Add the torrents and hit Magnetizer, it will start the torrent in your default torrent client. And yes, it can also be used to batch convert the torrents into magnet links.
Create or login into account and follows these steps: