Wing to wing and from the top of the grill to the bottom but don't include the splitter if you have one added... and preferably the depth of the bumper so how far it goes back from the front to the wing/wheel arch.
Sorry to be a pain it's just that I need to decide quite soon whether or not to buy a mk5 gti bumper or buy a standard lupo gti bumper, and my friend who works in the body shop said that the measurements would give me a better idea as to whether or not this could work.
I don't know anyone who owns a mk5 golf, my dad has a mk4 golf gti so no good...