Carat (ct) is the standard unit of weight used for Gemstones. Carats are divided into smaller units called Points. One Point (pt) is equal to 1/100 (0.01) of a Carat.
Diamond brokers sell diamonds with certain popular weights at a Premium, such as 1/2 ct (0.50), 3/4 ct (0.75), 1 Carat (1.00),etc. Save money by purchasing Diamonds that do Not have Exact popular weights. Such as 1/2 ct Light (0.46), 3/4 ct Heavy 0.79ct, 1 ct Light (0.90), 1 ct Heavy (1.11), etc.
Carat size is the least important of the 4 C's. The Cut, Clarity & Color of a diamond is more important when considering your diamond purchase. Quality is more important than Quantity.