According to one charity, Unicef, one million of those affected are children.
Help and supplies from all over the world are being flown into the country in South Asia. Nepal's government says it's doing all it can to help.
There's a lot to do: it's thought 1.4 million people are in need of food, the UN says.
Thousands in Kathmandu, Nepal's capital, spent a third night outside and water and electricity are in short supply.
The Nepal government has pleaded for overseas aid - everything from blankets and helicopters to doctors and drivers.
"We urge foreign countries to give us special relief materials and medical teams. We are really desperate for more foreign expertise to pull through this crisis," said a senior official.
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The country was hit by a massive earthquake on Saturday. At least 5,000 people have died and many people have been left homeless.
Nepal is a small country between India and China and is home to Mount Everest, one of the tallest mountains in the world.
It is also a very poor country and many of the houses there were not built to cope with an earthquake of this size.
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Aid agencies are using helicopters to get help and supplies to people who live in more remote mountainous areas, which are difficult to get to.
The priority for rescue agencies is to reach people who are trapped and injured, and provide shelter and protection to those who have lost their homes.
It's not just the towns and villages where people are in need of help. Hundreds have been rescued from near Mount Everest, the world's tallest mountain.
Even though the centre of the earthquake struck more than 120 miles away from the mountain it's had a major impact on climbers there.
Avalanches caused by the tremors have killed at least 18 climbers and injured more than 60.
Helicopters have been used to rescue mountaineers trapped on Everest.
Eight million people have been affected by the massive earthquake in Nepal - more than a quarter of the country's population - the United Nations says.