The world's biggest steel producer, which has had its credit rating cut to "junk" status, had forecast that the offer would raise $3.5 billion.
Lakshmi Mittal is the chairman and Chief Executive Officer of ArcelorMittal.
It issued $2.25 billion in convertible notes at a 6 percent yearly coupon, against a 5.875 percent to 6.375 percent range it gave when it announced the offering on Wednesday.
That compares with $1.75 billion it raised by selling shares at $16.75 each, a 4.4 percent discount to the price they closed at in the United States on Tuesday, the day before the offer was announced.
The Luxembourg-based group has stepped up its debt-cutting efforts since Standard & Poor's became the first credit agency to cut the group's rating to junk in August.