How far did Alexander the Great's empire actually stretch?

The answer

By the time of his death at age 32 in 323 BCE, Alexander the Great had created an empire stretching from Greece to northwestern India, covering over 5 million square kilometers - the largest empire the world had yet seen. He never lost a single battle, using innovative tactics like the oblique phalanx formation. His conquests spread Greek language and culture across Asia in a process called Hellenization, founding over 20 cities named Alexandria and permanently blending Eastern and Western civilizations.