YOU SAID:
My grandma farts louder than my mom
INTO JAPANESE
おばあちゃんはお母さんよりも大きい
BACK INTO ENGLISH
Grandma is bigger than mom
INTO JAPANESE
おばあちゃんはお母さんより大きい
BACK INTO ENGLISH
Grandma is bigger than mom
That didn't even make that much sense in English.