Tesla's CEO Elon Musk says he knows how many hours a week you need to work to change the world, and it's no small number.

The colourful entrepreneur says you need to be prepared to work more than 40 hours a week to make a big difference. Credit:AP

"There are way easier places to work, but nobody ever changed the world on 40 hours a week," he said in a tweet, after saying SpaceX, Tesla, Boring Company and Neuralink are the places to be if "getting things done matters to you."

When asked by a user exactly how many hours one had to work a week to change the world, he said 80 was a sustainable number, with peaks above 100 at times.

"Pain level increases exponentially above 80," he warned.