An Australian company has been awarded the contract to clean every window on the world's tallest building.

The company, Cox Gomyl, will use muscle-power and machines to keep the windows on Dubai's Burj Khalifa clean.

The Burj Khalifa, which was officially opened overnight, stands 828 metres high and has 200 storeys.

Dale Harding from Cox Gomyl says the company is taking on a massive task.

"There's around 24,000 windows in total, I think it's about 120,000 square metres of glass," he said.

"It's an amazing building, people focus on the height of the building ... but really the breadth and width of the building is just huge when you're standing next to it."

The tower has been named the Burj Khalifa after the ruler of the neighbouring emirate of Abu Dhabi, whose multi-billion-dollar bailout helped Dubai's biggest developer avoid a potentially disastrous debt default in November.