How do you call your Grand Father in American and British?

Question

I am doing a story and I want to know if you have any nick names for him

Answer 1

Papa
Grampa
Grandpa
I have used all 3 of these.

Answer 2

For Americans : Gramps, grand dad, grandpa
Quite often the grandparents' names are determined by the first grandchild's way of say grandfather such as "gaga" or a variation of their real name. If your character has a real name you could think of a way a child might say it and that usually becomes the name used by future grandchildren.