With 81 awards being given out, any award show that announced all of them live would take days. Add in all of the performances over the course of the night, and the show could take weeks. That's why they only announce 11 of the awards live on the show.
These 11 Awards are Record of the Year, Album of the Year, Song of the Year, Best New Artist, Best Pop Solo Performance, Best Pop Vocal Album, Best Rock Performance, Best Urban Contemporary Album, Best Rap/Sung Collaboration, Best Country Solo Performance, and Best Country Album
You can find a web ballot to make your predictions here from the Grammy Awards website.