As you see in the picture, you can fit three of these racks side by side, but you’ll have to remove the warming rack. As far as how many racks I can stack up, that would depends on the way I set it up and the height of the food that’s being cooked. Another word, it’s all about clearance. If you’re not using the grill original grates, then you can stack up more of these things. I’ve never used them for ribs, but I would guess each would hold 2 racks of ribs. I mainly use them for sausage and chicken parts.