As pure gold is too soft for everyday wear, gold jewelry often also contains other metals, such as silver, copper, nickel or zinc, to make the piece more durable. The karatage shows how much of the metal is pure gold, compared to other metals. 24k is 100% gold, while 18k is 75% gold, and 14k is 58.3% gold.
edit Difference in Appearance
It is almost impossible to tell the difference between 14k gold and 18k gold just by looking at them. However, experts say that the yellow color of 18k gold is more rich and vivid than in 14k gold.
14k gold is the most common type of gold in the US, and is used in approximately 90% of wedding bands. It is preferable for people who live more physically active lifestyles, as it is more durable than 18k gold.
18k gold is the most common type of gold used in Europe and Asia. As it is less resistant than 14k gold, it shows marks after less rough use.
edit Other Terms
As 14k gold is 58.3% gold, in Europe it can also be referred to as 583 gold. 18k gold can be referred to as 750 gold.
The value of 14k gold is calculated by multiplying its pennyweight by .583, dividing the current spot gold price by the number of pennyweights per ounce, and then multiplying the two values together.
The value of 18k gold can be calculated by multiplying the pennyweight by .750 and then following the same steps as above.
Prices of some gold jewelry are available on Amazon.com:
"14k Gold vs 18k Gold." Diffen.com. Diffen LLC, n.d. Web. 23 Nov 2014. < http://www.diffen.com/difference/14k_Gold_vs_18k_Gold >