Depends which variety you're asking about. The Progenitor Daleks are taller than the old-style bronze Daleks. Apparently, the old-style bronze Daleks were the right height to put the eyestalk at roughly the same level as Billie Piper's eyes. When they redesigned the things, they wanted the eyestalk to be on a level with Karen Gillan's eyes, and she's considerably taller. If you can find out the heights of the 2 actresses, you can probably work out the heights of the Daleks.