Karat (K) with a 'K'
Not to be confused with Carat (weight), Karat measures purity.
Pure gold is 24 Karat.
The Math of Karats
Because 24 is the base, you can calculate the percentage of gold easily:
- 18K Gold: 18/24 = 75% pure gold
- 14K Gold: 14/24 = 58.3% pure gold
- 10K Gold: 10/24 = 41.7% pure gold
Millesimal Fineness
Many modern jewelers use a 3-digit stamp instead:
- 750 = 18K (750 parts per 1000)
- 585 = 14K (585 parts per 1000)
- 417 = 10K (417 parts per 1000)
Why Not 24K Everything?
Pure gold is very soft. It scratches easily and can bend out of shape. Mixing it with other metals (alloys) like copper or silver makes it durable enough for daily wear.
Key Takeaways
- 24K is 100% pure (and very soft)
- 18K is the luxury standard for jewelry
- 14K is the most common for engagement rings