Gold karats: 24K, 22K, 21K and 18K

Parts out of 24

Karat measures gold as a proportion of 24 parts. 18K means 75% gold; the balance consists of alloying metals. Fineness expresses parts per thousand: 750 means 75%. 24K products may be marked 999 or 999.9; 22K is theoretically 91.67% (often 916 or 917), 21K is 87.5% (875), and 18K is 75% (750). Other recognized grades include 14K, commonly 585, and 9K, 375.

Higher is not always better for wear

Pure gold is relatively soft. Alloy composition, design, wall thickness and manufacturing all affect durability; a karat number alone cannot establish the strength of a thin ring. Country of manufacture and color do not prove purity.

Compare like with like

An 8 g 18K item theoretically contains 6 g of pure gold; an 8 g 21K item contains 7 g. Compare metal, making charges and stones separately. A hallmark is useful but does not replace a reliable invoice or professional testing when needed. Gold karat is purity; gemstone carat is weight.