Kalu was born to the family of Mr. Johnson Uzor Nesiegbe Kalu and Mrs Eunice Kalu. He attended Christ the King School Aba and Government College Umuahia. After studying at Barewa College, Zaria, he enrolled in the University of Maiduguri where he studied political science. During his time at the university, Kalu became a student activist, and participated in the "Ali Must Go"[4] riots against the education minister.[5] His participation resulted in his suspension. While his fellow students later took the school authorities to court, Kalu left school to build his own business.

With only $35 to his name that he had borrowed from his mother, Kalu began trading palm oil, first buying the oil from Nigeria's eastern regions and then selling it in the country's northern regions.[7] He then began buying and reselling furniture on a large scale.

Kalu eventually established SLOK Holding, a conglomerate that would consist of a number of successful companies, including the Ojialex Furniture Company, SLOK Nigeria Limited, SLOK United Kingdom Limited, Adamawa Publishers Limited, SLOK Vegetable Oil, Aba, SLOK Paper Factory, Aba, SLOK United States Incorporated, SLOK Ghana, Togo, Cotonou, Guinea, South Africa, Liberia, Botswana, SLOK Korea, Supreme Oil Limited, SLOK Airlines, Sun Publishing Limited, and First International Bank Limited.

Kalu became the youngest Nigerian to receive the National Merit Award from President Ibrahim Babangida, at the age of 26 in 1986. He was selected as the Nigerian Chamber of Commerce's Industrialist of the Year, and awarded the Humanitarian Award of the University of Nigeria, Nsukka's Humanitarian Club, the Volunteer Award of the International Association of Volunteers, the National Merit Award, the EU Special Award in Brussels, and the World Bank Leon Sullivan Award.

Kalu has a degree from Abia State University, a Certificate in Business Administration from Harvard University and honorary doctorates from the universities of Maiduguri and Abia State.