About University of Colorado Boulder. University of Colorado Boulder in Boulder, CO reports an overall acceptance rate of 75.9%, an early-round acceptance rate of 80.0%, an SAT middle 50% of 1180–1390, a class size of 7,106, and a yield of 16.0% based on the most recent Common Data Set filings. AAU flagship with top aerospace engineering and physics programs (CU Boulder has more astronaut alumni than most schools). Strong environmental science. Early acceptance rate ~84%.