Names for Grandparents: What do you call yours?

[BitsyNaceyDog]

I always called my grandparents "Grandma/Grandpa [last name]. I would have preferred it to be the same for Nathan, but my MIL insisted on being called Nana.

I still prefer adding the last name so my parents are "Grandma and Grandpa [last name]" and Justin's parents are "Nana and Grandpa [last name]".