Egypt's interim President Adli Mansour will address the nation on Sunday to congratulate the people on the approval of a new constitution.
Egypt's Supreme Judicial Committee for Elections said on Saturday that a constitution voted on last week has passed with 98.1 percent approval.
Egyptians voted last week in a referendum seen by the interim government and the majority of Egyptians as a stepping stone towards democracy, but by Islamists and some activists, who boycotted it, as illegitimate.
The committee said in a press conference on Saturday that 38.6 percent of Egypt's eligible voter population participated in the referendum, compared to last year's 32.19 percent turnout.
Only 1.9 percent of voters voted "no" to the constitution against the 19,985,389 people who voted "yes".
The overall turnout was 20,366,173.
The amended constitution will replace another written by an Islamist-led assembly under the Mohamed Mursi administration in 2012.
Egypt's army ousted Mursi in July in response to mass demonstrations against his rule, suspended his constitution and called for early parliamentary and presidential elections.
A Reuters report said earlier on Saturday that the interim president will call for presidential elections later today.
Defense Minister Abdel Fattah al-Sisi, who gained wide popularity after ousting president Mursi, is expected to win the race if he ran.
Sisi, who was hired by Mursi, is yet to announce whether he will run this year's presidential race.
Read the approved constitution here