For video size, encoder and Bit Rate of video are the most important points. In broad terms, the video size is determined by bit rate. Under the same resolution, the higher bit rate the video possesses, the bigger the video size is.
After the video compression, the size of source file and output file may differ widely due to the changes of encoder and bit rates. However, it is not wise to directly resize video for smaller size
by your own efforts if you're not familiar with it. You may seek help for some software like reduce video file size software, shrink video converter or video compression software.
Here you can download the professional “reduce video file size software - HD Video Converter Factory Pro” right now to have a try and you’ll find it’s usable.Method 1: Shrink Video Size with H.265 Encoder
Method 2: Reduce Video Size with Build-in Advanced Compressor Bar
Method 3: Cut Off Unwanted Part