An MKV file can get pretty large if it is an HD video file. It can reach in excess of ten to twenty gigabytes. If this is the case, and the device you plan on watching the file from does not support file sizes that big, you are going to need to split the file into a few different MKV files. MKVMerge does an excellent job at this and is freeware.
Download and install MKVMerge from the Resource section of this guide. MKVMerge is free software that allows you to create, split and join MKV files from other video file formats. Once the program is installed, open it by double-clicking the icon from your desktop.
Click the "Add" button on the top portion of MKVMerge. A new window will appear allowing you to search for your MKV file on your computer. Select it and click "Open" to load it into MKVMerge. Press the "Global" tab at the top of the program.
Click "Enable Splitting" from the "Splitting" section of the menu that appears. Here you can choose how to split the MKV file. You can split by size or time. If you select "After this size" click the drop-down box to select the size of each file split. If you are selecting "After this duration" click its corresponding drop-down box and select how long you want the MKV file's duration to last.
Click the "Browse" button at the bottom of the program and select where you want to save the new MKV files. Click "Save" when you have found the proper place, and press the "Start Muxing" button at the bottom of the program and your MKV file will be split into different parts according to your settings.
Wait as the program muxes the MKV file into its different parts. When it completes, locate your new MKV files from the location you designated in step four.