It's not the proper banana box hauler, but it can take 17 if you need it to.
The results are moderate, as the Model 3 was able to handle 6 boxes in the rear trunk and 17 total after folding seats and including one in the frunk. It's enough to beat the Volkswagen e-Golf, but worse than the Opel Ampera-e, old and new Nissan LEAF, as well as the Hyundai IONIQ Electric.
Overall, the trunk capacity of the Tesla Model 3 is reasonable, but we would bet that a hatchback/liftback would be better froma practicality perspective.
Results (trunk / with folded seats):
VW e-Crafter: 156/156 Nissan e-NV200: 50/50 Model X 5 seater: 10+1/28 Model S pre-facelift: 8+2/24 Model X 6 seater: 9+1/23 Audi e-tron: 8/23 Kia e-Niro: 8/22 Model S facelift: 8/22 Nissan Leaf 2018: 7/21 Kia Soul EV: 6/21 Jaguar I-pace: 6/20 Hyundai Ioniq: 6/18 Nissan Leaf 2013: 5/18 Opel Ampera-e: 5/17 Tesla Model 3: 6/17 VW e-Golf: 5/16 Hyundai Kona: 5/16 Mitsubishi i-MiEV: 3/16 VW e-up: 4/14 BMW i3: 4/14
Fiat 500e: 1/8