How old was Alexander the Great when he became king of Macedonia?

Alexander III of Macedon (20/21 July 356 BC – 10/11 June 323 BC), commonly known as Alexander the Great was a king (basileus) of the ancient Greek kingdom of Macedonia and a member of the Argead dynasty. He was born in Pella in 356 BC and succeeded his father Philip II to the throne at the age of twenty.

He spent most of his ruling years on an unprecedented military campaign through Asia and northeast Africa, and he created one of the largest empires of the ancient world by the age of thirty, stretching from Greece to north-western India. He was undefeated in battle and is widely considered one of history's most successful military commanders.

During his youth, Alexander was tutored by Aristotle until age 16. After Philip's assassination in 336 BC, he succeeded his father to the throne and inherited a strong kingdom and an experienced army. Alexander was awarded the generalship of Greece and used this authority to launch his father's pan-Hellenic project to lead the Greeks in the conquest of Persia.