Fractional Carat Weight

When you purchase jewelry where the diamond is already pre-set (as opposed to selecting your setting and selecting your diamond individually), the carat weight is often described in fractions (e.g. 3/4 carats).

What the novice diamond buyer may not be aware of is that when a diamond’s carat weight is expressed in fractions, the FTC allows by law a range for the diamond’s actual carat weight to fall in. In other words, the diamond you buy may weigh somewhat less than the fractional weight listed.

The Federal Trade Commission (FTC) has established guidelines for the range of diamond carat weights that a fraction can represent. The following table correlates fractional sizes with their decimal equivalent:

Fractional Carat Weight Decimal Range (carats)
1/4 0.21 to 0.29
1/3 0.30 to 0.36
1/2 0.45 to 0.59
3/4 0.70 to 0.84
1 0.95 to 1.10
1 1/4 1.20 to 1.29
1 1/2 1.45 to 1.55
2 1.95 to 2.05

The problem is, and what may not be immediately apparent, is that the price range for, say, a .95 carat diamond versus a 1.1 carat diamond can be into the thousands of dollars. Which means that if you’re buying a pre-set engagement ring you could be paying quite a bit more than if you bought the setting and diamond individually.

This is something to keep in mind when shopping for your engagement ring, whether online or at a brick-and-mortar store.