Amanda, it will not fit your lens. Yours is a 58mm I believe on the 18-55 (mine is anyway), and the 50mm lens is smaller.
thats what i thought.. how do you actually tell? i have a box for my 50mm sis it on that i wanna get a lens hood later on
it's written right on the end of the lenses. And you'll need an adapter for the 50mm to put a lens hood on, because it's an inside thread, and doesn't have the outside threads for the lens hood. The other one, the lens hood will screw right on. Right now, I only really use the hood on my longer lens (55-250).