We had an Ikea kitchen delivered, it took up our whole dining room. You are meant to lay everything flat so nothing warps, we laid everything flat hence the space.
The main thing to consider is if you have any tall/larder units, they are very heavy and take up quite a bit of space. If you only have wall and base units then these can be stacked quite easily.
All our base cabinets are pull out ones so each cabinet came with 3 drawers, one visible and two for inside. These were stacked high!
We actually went through the delivery afterwards and marker penned each item so it was easy to see what it was and we separated base units and wall units into two different piles, plus the corresponding doors. Plus I had two deep drawers and one shallow drawer per base cabinet so I marked up those too. We had cover panels, and infill panels (under the oven etc) too.
Keep hold of the receipt, copy it if you can so you don't lose it as when you are trying to find out what some random box is you can look down the list and find it. Plus you will know how many items make up the cabinet, ie my base cabinet had the carcass, door, drawer front, 1 shallow drawer and 2 deep drawers.
My extractor fan was Ikea and is one that totally hides in a fan cupboard, if you have this don't put let them put the bottom of the cabinet in as they have to take it out 