• On Monday, Hilary Duff announced that she's engaged to boyfriend Matthew Koma.
• The couple shared matching photos on Instagram, in which Duff is seen showing off her engagement ring.
• Speaking to INSIDER, representatives for RareCarat, a diamond search engine, said the ring is likely four carats, and could be worth $100,000.
• Visit INSIDER's homepage for more stories.

Hilary Duff took to Instagram on Monday to announce that she's engaged to boyfriend Matthew Koma. In her post, the "Younger" actress also gave fans a glimpse of her engagement ring.

"He asked me to be his wife," Duff captioned her Instagram photo, in which she's seen holding her left hand up next to Koma.

Speaking to INSIDER, representatives for RareCarat, a diamond search engine, said the ring likely includes a four-carat, cushion-cut stone that's worth $100,000.

The diamond experts at RareCarat also said the gem is likely a quality of G VS1 or higher, which stands for "Very Slightly Included," or including few flaws.

Read more: Hilary Duff and boyfriend Matthew Koma are engaged: 'He asked me to be his wife'

Duff and Koma have been linked since they made their first red-carpet appearance as a couple in January 2017. However, it's unclear as to when exactly they started dating. E News also reported that Duff and Koma broke up in March 2017, but eventually got back together — and have since shared much of their relationship on Instagram.

In October 2018, Duff and Koma also welcomed their first child together, a girl named Banks Violet Blair.

At the time, Koma said on Instagram that he and Duff were "grateful" for their "beautiful daughter, little sister, and best friend for life."

• Read more:
• Hilary Duff got real about how miserable it is to pump breastmilk and her 'emotional and hard' decision to stop nursing
• THEN AND NOW: The cast of 'A Cinderella Story' 15 years later
• Hilary Duff says she doesn't recognize herself after dying her hair an icy shade of 'winter white'
• Hilary Duff says she struggles to ignore mom-shaming on Instagram: 'Bullying seems to be at an all-time high right now'

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