Hahahah I have always laughed about this because it certainly seems like he would have fit - but in the movie he kind of tries to and it starts to capsize. My ultimate conclusion is that the door wasn't buoyant or stable enough for both of them. However, talk of this seriously cracks me up. Hahah

Recently before the 3D re-release, an article came out saying that a group of scientists have tested the theory. They got a replica of the board -- same shape, size, and weight -- and proved that even if both of them had balanced their weight, it would have sunk, thus giving them more exposure to the water. If it had sunk a couple inches, maybe they could've both survived, but this would've covered them and then maybe it would've tipped over as well.

yah scientifically but they could have altered the movie and made it a happier ending
i wish jack would have lived

If only Rose stayed in that lifeboat...

James Camern was on mythbuaters and they proved that that they both could have stayedon it but James said Jack had to die because it was in the script

They could both fit but since rose is so fat and could barely handle her weight it couldn't also handle jacks weight
They were both too heavy
It wasn't about how much space there was it was how much weight it could handle and the door started to sink when jack got on it