Minecraft wiki entry for Magma_Cube, associated text: A magma cube jumps a distance of approximately its length times 1.5 and a height equivalent to its size in blocks. This means that a large magma cube jumps 4 blocks in height and moves significantly quicker than a small magma cube, which jumps 2 blocks in height; while a tiny magma cube moves slowly and jumps 1 block in height.