Fineness of pure gold would be denoted as 1.000 fine. However, since absolutely pure gold is very soft and therefore not suitable for coinage. It is generally accepted worldwide that anything above .999 fine qualifies as 24K. Below is a conversion chart for karat weight to fineness.
Correlation between karats and fineness :
- 24 karats = .999 fine or above
- 23 karats = .958 fine
- 22 karats = .917 fine (the UK gold coin standard)
- 21 karats = .875 fine
- 20 karats = .833 fine
- 18 karats = .750 fine
- 16 karats = .667 fine
- 14 karats = .583 fine
- 10 karats = .417 fine
The fineness of pure gold coin is often converted to a percent, as well. If a gold coin has a fineness of .900, that is 90.0% pure gold. If a gold coin has a fineness of .850, then the gold coin is 85.0% pure.