Mind blowing! If you knew your mind could not handle it and you would implode that's right not explode implode bc the universe is so big it could crush you! but if you want a math magical answer imagine an 8 sideways!
109999093133887095609466049039054905990078738BIGi27674389109200002893281712187163762767627647672767326746791800009068909578478383001030405003059836763477452723890987654323456783952093011129384756473892011928376574389201982374654783921111128376457894748675612546787438984398594869548694397589328390808001294892999289478594308499289213020392094030493.000000000444444444444444499499278849839289382984928498948928499 miles wide
No one knows how big it really is, all we know is that its very big because we can never find the end. Many people say it doesn't have an end. And many people say it does but its so big that we can't find it, if you want to know more then check out the NASA website: http://www.nasa.gov/home/index.html
if you think of a balloon we are a little dot on the balloon and we are in constant moving of the galaxies since of the big bang there is no theory about the end of galaxy it is all a big balloon as it comes of it the universe its growing but not at a decisive speed no one know what speed its the Universe growing for and nobody knows how hard was the explosion of the big bang and what caused the big bang.