Can a half-carat diamond be an engagement center in the US?

Yes, if you like the size. It is a different object from a 1.5 carat center, so do not copy clarity and color advice across those weights.

US guides

Do not plan a US center stone with half-carat rules

Inclusions and tint that vanish at half a carat show up when the stone is three times heavier.

The US decision

Side stones should be chosen after the center, and matched to its color so the US ring does not look mismatched.

What to verify

If the half-carat stone is the center, judge it at that size on a hand, not against a 2 carat photo.

What to do next

Filter the carat you are actually buying. Carat Mate ships the certified loose diamond and its lab report to United States addresses. Prices on the site are in USD. Wrong-item returns may be considered within 3 days of delivery, subject to review.

Questions

Can a half-carat diamond be an engagement center in the US?: Yes, if you like the size. It is a different object from a 1.5 carat center, so do not copy clarity and color advice across those weights.