Widodo made the declaration at a news conference in south Jakarta after the total votes counted in quick count surveys carried out by 12 pollsters nearly touched 100 percent.
"Since yesterday (Wednesday) we have waited the quick counts surveys will give a clear result. But today the total votes counted is almost 100 percent."
"The result of 12 surveys showed Joko Widodo and Ma'aruf Amin secured 54.5 percent votes, and Prabowo and Sandi got 45.5 percent," said Widodo, referring to his rival Prabowo Subianto and his running mate Sandiaga Salahuddin Uno.
"As we know that the quick count survey is conducted scientifically. Based on experience in the past the results were accurate and nearly similar with that resulted by the real count," he said.
The president also said that he had received congratulations from a number of leaders of foreign nations.
Meanwhile, Widodo's rival Prabowo rejected unofficial results released by the five pollsters and claimed himself the winner with 62 percent votes based on results of his camp's internal polling body.
Official result of the election is scheduled to be announced on May 22.
Widodo, 57, a former furniture businessman who started his political career as mayor of Surakarta in Central Java and then as governor of Jakarta, defeated Prabowo in the 2014 polls.
