I got the basic cyclocomputer and I simply take note of my start time and divide the distance I've ridden an hour (or two) elapsed and consider that my avg speed. As of late, my rides are becoming longer where my rides are of a minimum of 3 hours. But, my speed suffers immensely after 1.5 hours. It's all relative though. Do not let the #s fool you. For all you know, some individuals ride on pancake flat while you're on rolling hills.