Trunk comparison: Audi A3 Sportback vs Mercedes Benz GLB

Main Differences

Trunk length with seats folded down: Mercedes GLB +11 in (19%) — the GLB offers significantly more cargo length when the rear seats are folded. Trunk length with front row seats upright: Mercedes GLB +7.1 in (23%) — even with full seating, the GLB retains more usable depth. Height of the trunk opening: Mercedes GLB +4.3 in (14%) — the opening is noticeably higher, allowing taller items and making it easier to load bulky cargo. Depth of the trunk (loading edge → floor): Audi A3 Sportback +1.6 in (33%) — the A3 has a deeper trunk floor relative to the loading edge, providing more space below the loading lip.

Impact on Usability

The greater length dimensions and higher opening of the GLB make it more practical for long or tall items (e.g., skis, planks, furniture parts) and for moves or larger luggage loads — both with folded and upright seats. The higher trunk opening reduces restrictions for bulky, tall cargo.

The A3 offers more usable volume below the loading edge due to the deeper trunk floor and a slightly lower center of gravity for the cargo.

In practice, this means: for heavy, bulky but not particularly long or tall loads (boxes, toolboxes, shopping), handling in the A3 is often more compact and more convenient with the lower loading edge (less lifting effort) — although the difference in loading edge height in favor of the GLB (+2 in) is under 10%.

In short: Those who regularly transport long or tall items or need maximum flexibility with folded seats benefit from the GLB. Those who mostly drive in urban areas, rarely load very long parts, and value easier lifting or a more compact cargo space will find the A3 more practical.