Offset splashed out over $500,000 on Cardi B's engagement ring.

Cardi B's engagement ring (c) Instagram

Cardi B's engagement ring (c) Instagram

The Migos rapper bought his new fiancee a stunning custom piece, featuring a eight-carat diamond surrounded by 2 half-carat pear diamonds and 2 carats worth of other pink and white stones from Pristine Jewelers in New York City and the lavish band cost him $550,000, TMZ reports.

The ring took a month and a half to make and was finished on the day Offset - whose real name is Kiari Kendrell Cephus - popped the question to Cardi while she was on stage at the Power 99's Powerhouse concert in Philadelphia last week.

The 'Bodak Yellow' hitmaker recently admitted she should have realised her fiance was planning to propose when he urged her to have a manicure.

She wrote on Instagram: "OK guys I know I keep posting about this day but I just can't believe it. I keep replaying it in my head. I keep smiling every minute.I should have known something was up since this n---- keep telling me to go get my nails done ...

"Like since when you cared about my nails. I love you and I love how you managed to get my mom to come out and witness my engagement. I'm the happiest girl in the world @offsetyrn you a true King (sic)"

Cardi was "so emotional" when Offset asked her to marry him and gushed about how he had encouraged her to follow her dreams.

The 25-year-old star shared at the time: "Jesus Christ I'm so emotional, @offsetyrn I loveee you so much .Thank you for seeing the potential in me since you met me .For giving me advice molding me and loving me .Your such a amazing man to me your family ,friends ,kids and you are extremely talented.I can't wait to spend FOREVAAAA with you .Lets make a lot shmoney and love together (sic)."