Taylor Swift's engagement ring is estimated to cost between approximately $250,000 and $1 million, with some expert opinions suggesting values potentially even higher depending on specific qualities of the diamond. The ring features a rare old mine-cut diamond, likely elongated cushion-shaped, weighing around 8 to 13 carats, set in 18-karat yellow gold with intricate vintage-style details. Valuations vary due to factors like the diamond's color, clarity, cut, and antique nature, with estimates ranging from about $120,000 on the low end to as much as $1 million or more if the diamond is particularly high quality and rare.