Measure your vehicle where the roof starts the steep curve to the rain gutter not from rain gutter to rain gutter.

The design of the "floating foot" allows vehicles to accommodate a wide variety of rack sizes. Each leg flexes and the feet rotate to adjust to the contour of the roof. The foot extends 1 1/2 " on each side beyond the wood of the rack

When we refer to the size of rack we are only referring to the size of the wood portion. You should add on 3" for the total but remember the foot flexes to adjust to the contour of the roof.