Will KALLAX Shelf unit, white, 30 1/8x57 5/8 " fit in an Audi A4 Avant 2022?

The A4 Avant pairs a wide mouth with real height: the opening measures 40⅛″ across and 33½″ tall, so upright boxes pass through without a tilt. The floor gives you 41⅜″ with the rear seats up and 72″ once they fold, a gain of 30¾″, with 39″ between the wheel arches at the tightest point. The lift-over sits at 24¾″ and the floor is only 2″ below it, almost level, so long boxes slide in instead of dropping in. Tall furniture cartons and long flat packs both do well here; extra-wide boxes meet the 39″ pinch first. Slide heavy loads across the sill on a blanket rather than lifting them over.

The KALLAX comes as a single flat carton, 59″ × 16″ × 6½″, and it carries real weight at 68 lb 5 oz for one box. It is a stiff, square-edged panel pack: not long enough to be unmanageable, but wide at 16″ and heavy enough that you will not want to hold it out at arm's length. A hatchback with the rear seats folded usually takes it, and an estate or SUV takes it without thinking. The weight is the thing to plan for. Keep it flat, slide it across the boot floor, and load it last.