How do I handle my husband insisting he is right?

Example: We have two bedrooms in the front of the house. One was a small office I used and the other was a bedroom my husband uses for his office. When I had the baby, I would have been happy to move my desk to the back guest room so my husband could move into the office. We would use the other bedroom for the new baby room. Husband, No doing. I moved my desk into the guest room and the baby went to the office. The baby has grown and needs a bigger bed, therefore bigger room. I asked again to change rooms. No doing - he insists they are the same size (i measured, they aren't) then he said the room he uses doesn't have any more "usable" space.....why is so insistant. I say take a left, he takes a right (it actually happened on a driving trip!...what is the scoop and how do I deal? He is driving me bonkers.