Lauren Conrad's engagement ring could be worth up to $40,000.

The reality star announced the news of her engagement to William Tell over the weekend by sharing a picture of her stunning diamond sparkler on her blog, which experts are claiming could have cost her law student beau a small fortune.

Zaven Ghanimian, marketing director of Simon G. Jewelry, told E! News: ''It's a four-prong, 2-carat round cut diamond with a thick band. It is tough to tell the price since the clarity and color can't be determined, but based on what we can tell it could range anywhere from $20,000 to $40,000.''

'The Hills' star has made a name for herself as a designer since the MTV programme ended in 2010, so her boyfriend of 21 months naturally opted for a trend-bucking ring for his fashion-forward fiancée.

Jewellery designer Jennifer Fisher - whose celebrity fans include Rihanna and Katie Holmes - said: ''Lauren's ring is quintessential timeless perfection when it comes to choosing a setting that will withstand the test of time. One quality about it that is exciting is that she has updated her gold colour to yellow, where there has been a trend for the platinum bands recently.''

Lauren's snapshot of her engagement ring caused a stir online and fans were also desperate to know where they could purchase the 'love' ring worn on her middle finger.

It has been revealed designer Sydney Evan is behind the elegant 14k gold creation, which is also owned by Julianne Hough and Khloé Kardashian.