This includes $200m of notes sold in an option exercised by the initial purchasers.
Initial purchasers have an option to buy up to an additional $62.5m in convertible notes by April 18.
Carnival said it expects to use the net proceeds from the offering for general corporate purposes.
Closing of 11.5% notes expected April 8
The closing of the company's previously announced private offering of $4bn of 11.5% first-priority senior secured notes due 2023 is expected to take place April 8.