How many grandchildren does Queen Elizabth II has?

Queen Elizabeth II has three great-grandchildren.

Peter Phillips, the son of her daughter Princess Anne and his wife Autumn are the parents of Savannah Phillips (born December 29, 2010) and Isla Phillips (born March 29, 2012).

Queen Elizabeth's grandson Prince William, Duke of Cambridge (son of Prince Charles), and his wife Catherine, Duchess of Cambridge, have a son, George Alexander Louis, Prince of Cambridge, who is third in line to the throne.