Lesson 7 · Diamonds explained · 42 seconds
Total carat weight. Explained.
"One carat total" is not always one big diamond. The number can describe one stone, two matched earrings, or several stones in a single piece. Learn to read it before you buy.
What this lesson shows
ct tw adds every diamond in the piece.
A single 1-carat round is about 6.4 mm across. A 1-carat-total pair of studs is about 0.5 carat per earring (about 5.1 mm each) and the two may not weigh exactly the same. A 1-carat-total three-stone piece can be a 0.5 carat center plus two 0.25 carat sides.
All three listings can say "1 carat total." They look very different in person.
Three quick takeaways
How to read ct tw on a listing
- Check whether the listed carat is for one stone, one piece, or the pair. If it says "ct tw" (total carat weight) you are reading the total.
- Total carat weight adds the relevant stones together. For a pair of single-stone studs totaling about one carat, each stone is approximately half a carat (not two one-carat stones); other earring designs can include multiple small stones per earring, in which case the per-stone weights can differ. Always check the listing.
- Three-stone and halo pieces often list center-stone carat separately from ct tw. Both numbers matter.
The pieces in the lesson are hypothetical computed models used to compare how the same ct tw can describe different pieces. They are not photographs of specific products.
Read the transcript
One carat total. Does that mean one big diamond? Not always. Total carat weight is every diamond in the piece added together. A single one-carat round is about six and a half millimeters across. A one carat total pair of studs is about half a carat per earring, about five millimeters each. And the two may not weigh exactly the same. This three-stone piece is also one carat total: a half-carat center and two quarter-carat sides. So check whether the weight means one stone, one piece, or the pair. Save this before you compare listings.
Sources
- GIA 4Cs, "Nine things about diamond carat weight you need to know": total weight of all diamonds in a multi-stone piece; typical dimensions for well-cut rounds. 4cs.gia.edu
- FTC 16 CFR 23.18 (Guides for the Jewelry Industry), "Misrepresentation of weight and 'total weight'": fractional representations must disclose that stones are not of the exact weight shown, or state a range or tolerance. law.cornell.edu/cfr/text/16/23.18
- Blue Nile, diamond stud earrings guide: stud pairs are typically sold by total carat weight. bluenile.com
Related lessons
See same carat, different look for why two 1 ct stones can measure differently across, and lab-grown vs CZ for how to confirm you are comparing diamond to diamond.
Next step
Shop diamond earrings and three-stone pieces.
Every Aydins lab-grown diamond listing shows ct tw alongside per-stone carat where it applies, so you know exactly what you are buying.