If you know the bitrate of your network or dialup connection and you know how much time you have on that line, the calculator will determine the maximum file size that can be transmitted across the line. Alternatively, if you have the file size and bitrate, the calculator will determine how long it will take to transfer the file. Lastly, if you know the file size and the time available for transfer, the calculator will determine the bitrate required to transfer the file in the given time period.