There are 100 points in a one carat diamond (written as 1.00 carat). ... A 10 point diamond is 1/10 of a carat or 10 points. A 1.50 carat diamond is one carat and a half, or a full carat and 50 points (150 points in all). So then when you see a . 38 carat diamond, you'll know it's a little more than 1/3 carat (.Dec 1, 2018