He doesn't know for certain. Even if he ever knew the exact measurements - Gaster hadn't exactly seen the need to share them - he couldn't recall them now.

So Sans shakes his head. The only thing he can think to say for certain is: "Bigger than you."

In the strange, mad, feverish way of those mired in panic and pain, he feels a pang of regret that she won't be able to pick him up anymore.