Purity explained
Gold Purity Chart and Karat Guide
Karat tells you how much of an alloy is theoretically gold. Use this quick guide to understand the factors behind 24K, 22K, 18K, and other gold value calculations.
Common gold purity factors
The calculator models purity as karat divided by 24. That gives a transparent estimate of fine-gold content before premiums, labour, testing, fees, or condition are considered.
- 24K = 24/24 = 1.000 theoretical factor
- 22K = 22/24 = approximately 91.67%
- 18K = 18/24 = 75%
- 14K = 14/24 = approximately 58.33%
- 10K = 10/24 = approximately 41.67%
- 9K = 9/24 = 37.5%
How purity changes a spot estimate
First convert the selected weight into grams, multiply by the 24K spot value per gram, and then apply the selected purity factor. The result is a theoretical spot / melt value estimate, not the price of a piece of jewellery or a guaranteed resale amount.
Fineness and real items
Real products can vary by alloy standard, hallmark, manufacturing, and testing result. A buyer or dealer may also apply a spread, refining cost, labour charge, or margin. Confirm the item's purity independently before using any estimate for a transaction.