The estimate was based on an assessment study by Iraqi and worldwide experts, the minister told the opening session of the three-day conference.
About $22 billion will be required in the near future and another $66 billion later, the director-general of the country's Planning Ministry, Qusay Abdulfattah, told the conference, without indicating a time frame.
The International Conference for Reconstruction of Iraq kicked off on Monday under the auspices of Emir of Kuwait Sheikh Sabah al Ahmad al Sabah.
The United States will be a main absentee from plans to contribute to Iraq's finances, USA officials say as Baghdad seeks to rebuild the country following a devastating battle against the Daesh Takfiri terrorist group.
Iraq declared victory over Islamic State in December, having taken back all the territory captured by the militants in 2014 and 2015.
About 2.5 million Iraqis remain displaced by the fighting, he added.
Authorities from worldwide organizations and foreign nations crowded into conferences in Kuwait City on Monday.
Kuwait's state news agency, KUNA, reported a pledge of providing Iraq with $330 million in humanitarian aid by non-governmental organizations at a parallel NGO conference. If you believe in collaboration to produce quality neutral journalism for everyone, it is important that you sign up to support our work financially.
"The government came out and said: we are serious about reforms. they know they need to give confidence to the global community that Iraq is a new country, a new place to invest and that will be protected and safe", said Ms Grande. We will always be there.
Authorities say they will need $88 billion to rebuild Iraq. We were there to participate in the coalition (against IS).
"If the global community doesn't help the government of Iraq to stabilize these areas (devastated by the war) the gains against ISIS could be at risk", she said.
Tillerson said Washington had also made a decision to provide an additional $200mn to stabilise liberated areas in Syria.
Iraq reopened to foreign investment after the 2003 US invasion, but the vast majority of the billions of dollars invested went to increasing its oil and natural gas production.
"The U.S., which has already spent billions of dollars on the war against ISIS and in providing aid to displaced Iraqis and Syrians, doesn't intend to donate funds for Iraq's reconstruction", pointed out WSJ.