Trunk comparison: BMW X3 vs Mercedes Benz GLB
Summary of the Biggest Differences
The clearly noticeable differences are with the Mercedes‑GLB: The height of the trunk opening is 3.5 in (≈11%) larger on the GLB and the depth of the trunk (loading edge to trunk floor) is 4.7 in (≈1100%) larger on the GLB.
Other, smaller differences: The trunk length with folded seats is slightly +0.4 in (1%) longer on the BMW X3; with the first row upright, both lengths are the same.
The loading edge of the GLB is +0.8 in (3%) higher than on the X3. In width, the BMW has +2 in (5%) more space at the narrowest point and +2.4 in (6%) more at the opening than the GLB.
Impact on Usability
Higher trunk opening (+3.5 in, GLB): The larger opening makes it easier to maneuver taller or bulky items into the interior. Loading and unloading bulky cargo (e.g., furniture, large boxes, or bulky sports equipment) is generally easier with the GLB.
Deeper loading floor (loading edge ↔ trunk floor, +4.7 in, GLB): A significantly greater depth means more usable interior volume behind the loading edge. This is advantageous for tall or stackable luggage and increases effective cargo capacity.
At the same time, a deeper loading floor can make lifting and repositioning heavy items more difficult because they must be pushed further into the space or lowered further.
Combined with the only slightly higher loading edge (+0.8 in), loading remains practical, but for very heavy or awkward loads, the X3 concept with less depth may be somewhat more comfortable.
The slightly greater width of the BMW (at the narrowest point +2 in, opening width +2.4 in) favors loading wider items and makes storing bulky cargo easier, even if these advantages are proportionally smaller.
The practically identical trunk length with the first row upright means comparable everyday usability for longer items; the minimal advantage of the X3 with folded seats (+0.4 in) is negligible.
Conclusion: The GLB offers more volume and better handling of tall or bulky loads due to the higher opening and significantly greater depth. The X3 scores slightly in width and ergonomic handling of very heavy, wide items.
Which variant fits better depends on the typical usage profile: lots of volume and bulky/tall cargo → GLB; more frequent transport of wide, heavy single items with easy handling → X3.