Gold karat is a way of expressing purity on a 24-part scale. In a calculation, 24K is the pure-gold reference, while a lower karat means that a smaller proportion of the item's weight is represented as pure gold.
Karat is a ratio
A useful calculation is: karat ÷ 24 = pure-gold proportion. For example, 22 ÷ 24 is approximately 0.9167, or 91.67%.
24K, 22K, 20K, 18K and 14K compared
The table below shows the mathematical karat ratio used for gold-content calculations. Rounded percentages are shown for readability.
| Karat | Ratio | Approx. purity | What it means |
|---|---|---|---|
| 24K | 24 / 24 | ≈ 100% | Highest karat in the common 24-part system. |
| 22K | 22 / 24 | ≈ 91.67% | Common reference purity for many gold jewellery calculations. |
| 20K | 20 / 24 | ≈ 83.33% | Contains less pure gold per gram than 22K. |
| 18K | 18 / 24 | 75% | Three-quarters pure gold by the karat ratio. |
| 14K | 14 / 24 | ≈ 58.33% | Lower pure-gold proportion than 18K or 22K. |
How purity changes gold value
Gold Ledger starts with a 24K reference rate and applies the karat ratio when estimating the gold-content value of a lower-purity item. This keeps the relationship between weight, purity and rate visible.
Start with weight
Use the gross gold weight entered for the calculation.
Apply purity
Convert the selected karat into its 24-part purity ratio.
Apply the rate
Use the reference gold rate to estimate gold-content value.
How much pure gold does 20g of 22K represent?
22K purity ratio = 22 ÷ 24 ≈ 0.9167
20g × 22 ÷ 24 ≈ 18.33g of equivalent pure-gold content.
This is a mathematical purity conversion. It does not verify the physical composition of a real jewellery item.
Purity is not the same as jewellery price
Purity helps estimate the gold-content portion of value.
A jewellery retail price can also include making charges, taxes and other commercial components.
An old-gold or resale quote can differ from theoretical gold-content value because the buyer may apply its own assessment, deductions or commercial terms.
If your goal is to estimate a monetary amount, continue with the Gold Value Calculator.
Can Gold Ledger determine whether gold is really 22K?
No. Gold Ledger performs calculations from the purity you select or enter. It does not inspect, assay or physically test gold, and it cannot authenticate a hallmark.
That distinction matters when using an online calculator: mathematical purity conversion can explain a stated karat, but the actual composition of an item requires appropriate physical verification.
Frequently asked questions
What does 22K gold mean?
In the 24-part karat system, 22K represents 22 parts gold out of 24 by the karat ratio. That corresponds to about 91.67% pure-gold content for calculation purposes.
Is 24K gold exactly 100% pure?
The karat ratio treats 24K as the pure-gold reference. Real-world fineness and product specifications can be expressed more precisely, so the displayed karat label should not be treated as a laboratory purity test.
Why does 18K gold have a lower gold-content value than 22K?
For the same gross weight and the same 24K reference rate, 18K contains a smaller proportion of pure gold than 22K. Its theoretical gold-content value is therefore lower.
Can a calculator tell me the actual purity of my jewellery?
No. A calculator can convert a purity or karat value that you provide, but it cannot physically test jewellery or verify whether a hallmark or stated purity is accurate.