The Palestinian Central Bureau of Statistics released the figures on the eve of Nakba Day, the Palestinian WAFA news agency reported.
Nakba Day, or "the day of catastrophe," marks the anniversary of the day hundreds of thousands of Palestinians were expelled from their homes after Israel became an independent state.
Data from the PCBS said 44.2 percent of the Palestinian population in the Palestinian territories was comprised of refugees.
The United Nations relief agency for Palestinian refugees said there were 5.3 million registered Palestinian refugees, representing 45.7 percent of all Palestinians worldwide, the Palestinian agency said.
Some 59 percent of refugees live in Jordan, Syria and Lebanon, while 17 percent are in the West Bank and 24 percent in the Gaza Strip.
The PCBS said 1.4 million Palestinians lived in 1,300 Palestinian towns and villages in 1948 when Israel became a state. The report said more than 800,000 people were driven out of their homes and into the West Bank, Gaza Strip, neighboring counties and other parts of the world.
Based on current growth rates, the population of Palestinians living in the Gaza Strip and West Bank is expected to rise to 7.2 million by 2021, the PCBS said.