Do two twin sized beds put together equal the size of one full sized bed?

I desperately need a new matress and to throw out my two twin sized matresses which are very old. Is "full size" the equivalent of two twin sized matresses when placed together or no? Thank you.
Update: Oh okay its like a King sized bed well that sounds fine too. I guess I have to order a King sized mattress although I would prefer a Queen sized mattress :)
Thanks for the answers, I appreciate the answers that are longer than one word.
Update 2: Well thanks for clarifying that it doesnt equal the size of a king sized bed, in fact its only slightly larger than a full sized mattress or slightly smaller than a QUEEN sized bed which is what I desired in the first place. Thank you, you will probably get best answer :)
9 answers 9