The provisional results of Nigeria's first census in 15 years show that Africa's most populous nation has a population of more than 140m.
Nigeria's oil wealth is distributed according to the population
The National Population Commission said this was an increase of 63% since 1991.
The headcount is sensitive, as funding and political representation for Nigeria's states depend on the results.
Previous results have been mired in controversy and allegations of fraud, but March's census left out questions on religion and ethnicity.
The government was concerned that such information would trigger ethnic riots.
The National Population Commission (NPC) chairman said this time he felt there would be no problems.
"I don't expect any controversy because we have done a transparent and credible census. We have done it as honestly as we can, using the most scientific methods of census taking," Sumaila Makama told the BBC's Focus on Africa programme.
The BBC's Mannir Dan Ali in the capital, Abuja, says the big surprise in the results so far is that Nigeria has three million more men than women.
The last census put Nigeria's population at about 88.5m.
"I am not alarmed about the total figure because it is still within the range of what we are planning," President Olusegun Obasanjo said.
Our correspondent says most Nigerians are more interested in finding out the regional and local spread of the population - figures that have not been revealed yet.
The census questionnaire was two pages long
The higher a state's population the more money it gets from the federal government.
Allocation of some government posts is also supposed to reflect different regions' populations.
But Nigerians must wait until the president, state governors and former heads of states have met to consider and agree to these figures.
Many people had wanted to find out how many Christians and Muslims there are in Nigeria, our reporter says.
But that aspect was left out of the census questionnaire.
Past censuses have generated so much controversy that many of them have been officially discarded, leaving Nigeria to use estimates for planning purposes.
The counting operation in March was a logistical challenge for the NPC.
It used digital processing of the forms, and satellite positioning to identify the areas to be counted.
Other questions included in the census were:
- Education background
- Size of house
- Type of water supply
- Toilet facilities
- Type of fuel used
- Access to radio, television, telephone