text: how big is the universe? i have heard from somewhere that universe is 9,737,608,990,000 miles big which is 9.7 trillion miles, or 15,671,162,600,000 kilometers big which 15.67 trillion kilo meters. is it true? it is constantly expanding.  so it is impossible to give an accurate sizing that will last for more than a few moments in time.  sadly, because of the size of the universe and the vast number of light years that it is across, by the time we figure out how big it is at any given time in our relative timespace the universe has already expanded exponentially.