A Carat Is 1/24th By Weight
Don't confuse the word "carat" as used for diamonds or other gemstones, when it is a unit of weight.
A carat as applied to gold alloys means a proportion by weight of one part in twenty-four, or 41.66 parts per 1000. The higher the carat value, the higher the proportion of gold in relation to the base metal content. Pure gold is therefore 24 carat.

Percentage by Weight
The following table shows typical "recipes" for different common gold alloys.

Percentages by Weight
Alloy	Gold	Silver	Copper	Zinc	Nickel	Palladium
9 Yellow	37.5	10	45	7.5	-	-
9 White	37.8	0	40	10.4	11.8	-
14 Yellow	58.5	4	31.2	6.3	-	-
14 White	58.5	0.5	27	7	7	-
18 Yellow	75	16	9	-	-	-
18 White	75	4	4	-	-	17
22 Yellow	91.7	5.5	2.8	-	-	-
24	100	-	-	-	-	-