A sim rig’s dimensions tell you where the frame will sit. You still need room to pull the seat back, swing your legs in, and plug in a USB cable after the rig is against the wall. A roll of painter’s tape can settle those questions before anything ships.
Mark the space you’ll use
Tape the cockpit’s outer dimensions on the floor. Mark the pedal end and the side you’ll enter from. Use a chair to approximate the seat and walk through getting in and out. If the setup will be shared, have the tallest and shortest drivers try it. Check the path from the doorway too, especially if you’ll assemble the rig in another room.
Now mark the monitor stand’s feet, if it has its own stand. Allow space for the screen and any connectors that stick out behind it. Open nearby drawers and doors. A cabinet door that clears the bare frame might hit the edge of a screen or a shifter arm.
Keep the connections within reach
Pick a spot for the PC or console where you can reach its ports and keep its vents clear. Trace the path from pedals and wheelbase to that spot with string. Follow the route the cables will actually take around uprights and along rails. That measurement is more useful than the straight-line distance across the room.
Take a photo of the taped layout with the main measurements written down. Compare it with the drawings for the cockpits you’re considering. It gives you a quick way to check the fit again if you change the screen, seat, or mounting side.