i'm 5'11" but with short legs. i always read that you stand over the frame on tip-toes in front of saddle, there should be about 3 inches between you & top tube. so i got me a 17" muni mula.
also look at pictures of bikes. some are measured to top of top tube, or top of seat tube, & some frames have extended seat tubes.
other things to consider are stem length / rise, & crank length.