2018 Kia Soul: 18.8 Cubic Feet

Though the Kia Forte5 isn’t the best-selling vehicle on this list (and it probably won't stick around with the arrival of the new sedan), it’s one of the most spacious. It bests the Soul – which the NHTSA classifies as a small SUV – in both rear cargo room and total volume. The Forte5 has 23.2 cubic feet of room behind the third row, and 56.4 cubic feet with the rear seats folded flat.