Freemake Video Converter is free software to rotate video. Rotate videos from iPhone, PC, cellphone or camcorder 90, -90, 180 degrees easily. 250+ video formats supported: AVI, MP4, WMV, MKV, FLV, DVD, etc. Download freeware here.
Look for the video you want to rotate using the "+Video" button or drag-'n-drop option.
Click "Edit/Play" button on the right. Click the button "Rotate 90° CCW" or "Rotate 90° CW" to turn your video left or right respectively. Click "Ok".
To save the changes, you have to convert the video. Choose a format (better the same as the original), preset "Same as source", and click "Convert". Watch on YouTube our video guide "How to rotate video".