Terminology reference
Karat vs.
carat.
They sound identical, but they measure entirely different things. In U.S. jewelry terminology, karat describes gold purity; carat describes the weight of diamonds and other gemstones.
The difference between karat and carat
Gold purity
Karat
Measures how much pure gold is present in a gold alloy.
- Scale
- 24 parts
- Example
- 18K = 18 parts gold + 6 parts other metals
- Purity
- 18 ÷ 24 = 75% gold
Gemstone weight
Carat
Measures the weight of diamonds and most other gemstones—not their physical dimensions.
- Standard
- 1.00 ct = 200 milligrams
- Points
- 1 carat = 100 points
- Example
- 0.50 ct = 50 points = 100 milligrams
Reading a specification
Both can appear
in one sentence.
The surrounding words and abbreviations show whether the number describes the metal or the stone.
14K yellow-gold solitaire ring with one 1.00 ct round diamond.
Gold purity: 14 of 24 parts are gold.
The color family of the gold alloy.
The diamond weighs 200 milligrams.
The diamond’s shape—not its weight or quality.
Avoid common confusion
What the number
does not tell you.
Karat and carat communicate one specific measurement each. Neither number, by itself, describes the complete quality, durability, appearance, or value of a finished piece.
Higher carat does not mean higher quality
Carat records weight. A diamond’s overall quality and value also depend on cut, color, and clarity.
Equal carat weights can look different
Shape, cut proportions, and gemstone density can change the visible dimensions of stones with the same weight.
Higher karat means more gold
It does not automatically mean the finished piece is stronger. Alloy composition and construction also affect performance.
Total carat weight combines stones
When several stones are used, total carat weight refers to their combined weight—not the weight of each individual stone.
Reference standards: U.S. Federal Trade Commission guidance on gold jewelry and GIA guidance on carat weight.