Synset

spatial largeness and extensiveness (especially inside a building)
<noun.attribute>   freq. cnt.: 2 freq. cnt.: 2

capaciousness

commodiousness

roominess

spaciousness

sample sentences

"the capaciousness of Santa's bag astounded the child"
"roominess in this size car is always a compromise"
"his new office lacked the spaciousness that he had become accustomed to"