Gold purity explained
Gold purity is measured in karats.
The karat (US spelling, symbol K or kt) or carat (UK spelling, symbol C or ct is a fractional measure of purity for gold alloys, in parts fine per 24 parts whole. The karat system is a standard adopted by US federal law
24-karat gold is pure (while 100% purity is unattainable, this designation is permitted in commerce for 99.95% purity), 18-karat gold is 18 parts gold, 6 parts another metal (forming an alloy with 75% gold), 12-karat gold is 12 parts gold (12 parts another metal), and so forth.
In England, the carat was divisible into four grains, and the grain was divisible into four quarts. For example, a gold alloy of 127⁄128 fineness (that is, 99.2% purity) could have been described as being 23-karat, 3-grain, 1-quart gold.
The karat fractional system is increasingly being complemented or superseded by the millesimal system, described above.
Conversion between percentage of pure gold and karats:
- 58.33–62.50% = 14K (acclaimed 58.33%)
- 75.00–79.16% = 18K (acclaimed 75.00%)
- 91.66–95.83% = 22K (acclaimed 91.66%)
- 95.83–99.95% = 23K (acclaimed 95.83%)
- 99.95–100% = 24K (acclaimed 99.95%)