Sometimes we use the verb "double",e.g., "he doubled my pocket money", and sometimes we use "triple" as verb- but what is the verb when the issue is about getting 4 times or 4x of a thing.
The word you are looking for is Quadruple.
Commerzbank, Germany's second biggest bank, said Friday that its profits quadrupled in 2015 and it would resume...
The series continues from there, double, triple, quadruple, quintuple, sextuple, septuple, octuple... but after quadruple, the terms are less and less common. I don't think I have ever used anything past quintuple.
Similar is four-fold:
My hair grew from 2 inches to 8 inches in one month. A four-fold increase!
Fourfold both work. They are both adjectives, although Quadruple is more common.
Go to this page for a full list of tuples. (words for 5x, 6x, etc)