Trunk comparison: BMW X3 vs Volvo XC40

Key Differences
There is no deviation between the two models exceeding 10%. The biggest differences in favor of the BMW X3 are: 3.5 in (9%) wider at the narrowest point, the trunk opening 2.4 in (8%) higher, and the Volvo's loading edge is 2 in (7%) higher above the ground (thus, the BMW has the lower loading edge).
Other differences: the BMW offers 3.9 in (6%) more length with the seats folded down and a 2.4 in (6%) wider opening; with the rear seat upright, the BMW is 1.6 in (4%) longer. The depth (loading edge to trunk floor) is the same.
Impact on Usability
Due to the greater width at the narrowest point and the wider opening, the BMW X3 is better suited for wide or bulky cargo (e.g., furniture parts, strollers, or large boxes).
The higher trunk opening of the X3 makes it easier to load tall items in the rear area. At the same time, the lower loading edge of the X3 makes lifting heavy loads into the trunk easier than with the XC40.
The differences are overall moderate (none >10%). For frequent transport of very bulky or tall items, the BMW offers noticeable advantages. For normal everyday use (shopping, luggage, occasional transports), both models are largely equivalent in practice.