I know that w/o the sm card the camcorder can only have a memory of about 27 seconds and with it, the memory is extended, but im not sure by how much. I want to record my sisters graduation, but im not sure if one sm card is enough to cover the whole thing

i think you mean SD ? , its better to get a tape or HDD because memory cards dont hold that much data and the main use if still photos but if your using then for video get a few and make sure you label them and get large ones like 1 or 2 GB