By the Silver Gold Today Editorial Team. Reviewed through our editorial process. This article is general education. It is not financial advice and not licensed financial advice. Silver Gold Today may earn a commission from some links on the site; see our affiliate disclaimer.
Karat marks such as 10K, 14K, 18K, and 24K appear on most gold jewelry and on some coins. They describe how much of an item is gold. With gold karats explained clearly, it becomes straightforward to estimate gold content, compare prices across items of different purity, and understand why higher purity is not always better for everyday wear. This analysis sets out how the karat system works, how to convert karats to gold content, and what the differences mean for value and durability.
Key points
- A karat expresses gold content in twenty-fourths: 24 karat means all 24 parts are gold.
- Gold content as a fraction equals the karat number divided by 24.
- Lower-karat gold contains more alloy metals, which affects colour, hardness, and value.
- In the United States, the FTC’s Jewelry Guides address how karat marks may be used.
How the gold karat system works
The karat system divides an item into 24 parts and states how many of those parts are gold. A 24-karat item is, in principle, entirely gold. An 18-karat item has 18 parts gold and 6 parts other metals. The remaining metals form an alloy with the gold, adding strength and changing colour.
Karat (sometimes spelled carat in British English when referring to gold) should not be confused with carat as a unit of weight for gemstones, which is a different measure entirely.
In the United States, the Federal Trade Commission’s Guides for the Jewelry, Precious Metals, and Pewter Industries (16 CFR Part 23) address how sellers may use karat marks and gold descriptions. Readers who need the precise rules should consult that text. Other countries have their own hallmarking and labelling systems.
Converting karats to gold content
Gold content as a fraction is simply the karat number divided by 24. The table shows the arithmetic for common karat levels, rounded to one decimal place.
| Karat mark | Calculation | Gold content (approx.) |
|---|---|---|
| 24K | 24 ÷ 24 | 100% |
| 22K | 22 ÷ 24 | 91.7% |
| 18K | 18 ÷ 24 | 75.0% |
| 14K | 14 ÷ 24 | 58.3% |
| 10K | 10 ÷ 24 | 41.7% |
These are arithmetic conversions of the karat definition. Actual items may contain marginally more or less gold within manufacturing tolerances, which is one reason professional testing remains useful for valuable pieces.
Karats and fineness marks
Some items show a fineness number instead of, or alongside, a karat mark. Fineness expresses gold content in parts per thousand. Multiplying the karat fraction by one thousand gives the corresponding fineness, so an 18-karat item corresponds to roughly 750 parts per thousand. Both systems describe the same thing in different units.
Calculating gold value from karat
To estimate the gold value of a jewelry item, we use three steps:
- Weigh the item in grams using an accurate scale, ideally excluding gemstones and non-gold components.
- Multiply by the karat fraction (karat ÷ 24) to find the weight of pure gold.
- Convert to troy ounces and multiply by spot. Divide the gold weight in grams by 31.1034768, the NIST definition of a troy ounce, then multiply by a live gold spot price from a source such as Kitco.
The result is the melt value. Buyers of scrap gold typically pay less than melt value to cover testing and refining. Our guide on how to sell gold and silver explains how to compare offers.
Worked example with invented figures
The figures below are invented to show the arithmetic. They are not current prices.
Suppose a 14-karat chain weighs 20 grams and spot is 100 units per troy ounce. The gold weight is 20 × (14 ÷ 24) ≈ 11.67 grams. In troy ounces, that is 11.67 ÷ 31.1034768 ≈ 0.375. The melt value is therefore about 37.5 units. The same weight of 18-karat gold would contain about 15 grams of gold and have a melt value of about 48.2 units.
Purity, colour, and durability
Higher karat means more gold, but not necessarily a better item for every use. In our analysis, three trade-offs matter:
| Factor | Higher karat | Lower karat |
|---|---|---|
| Gold content and metal value | Higher | Lower |
| Hardness and scratch resistance | Lower; softer metal | Higher; more alloy |
| Colour | Deeper yellow | Varies with alloy; can be paler or tinted |
Pure gold is soft, which is why many everyday pieces use lower karats for durability. Alloy choice also creates colours such as white gold and rose gold, which depend on the metals mixed with the gold.
Comparing prices across karats
Retail jewelry prices usually include design, labour, and retail margin as well as metal content, so two items of the same weight and karat can differ widely in price. To compare items fairly, we suggest calculating the price per gram of pure gold: divide the item’s price by its gold weight (total weight multiplied by the karat fraction). This shows how much of the price reflects gold and how much reflects other factors. A higher-karat item can turn out to be better value per gram of gold even with a higher sticker price, or the reverse, depending on design and labour charges.
Karats in coins and bars
Bullion bars and many bullion coins are described by fineness rather than karat. Some coins are alloyed for durability, so their gross weight exceeds their gold content. Valuation should always use the stated fine gold content. Our guides to gold bars vs gold coins and troy ounce vs ounce cover these points.
Checking karat marks
Karat stamps usually appear on clasps or inner surfaces. Marks can be worn, missing, or occasionally inaccurate. For items of meaningful value, we recommend testing by a reputable jeweler or dealer. It is also important to distinguish solid gold from layered constructions; see solid gold vs gold-filled vs gold-plated. A written receipt that states the karat gives the buyer a record if a later test shows a discrepancy.
Where an item has no visible mark at all, we suggest treating its karat as unknown until it has been tested. Estimating purity from colour alone is unreliable, because alloy metals can make lower-karat gold look richer or higher-karat gold look paler than expected.
Frequently asked questions
Is 24K always better than 18K?
24K contains more gold and has higher metal value per gram, but it is softer. For everyday jewelry, lower karats are often chosen for durability.
How do I convert karat to percentage?
Divide the karat number by 24 and multiply by 100.
Does a karat mark guarantee purity?
A mark is a seller’s representation. Professional testing is the reliable check for valuable items.
Is karat the same as carat?
For gold purity, the terms are sometimes used interchangeably. For gemstones, carat is a unit of weight, which is unrelated.
Methodology and sources
Gold content figures are arithmetic conversions of the karat definition (karat ÷ 24). Unit conversions use the NIST definition of the troy ounce. US labelling references the FTC Jewelry Guides. The worked example uses invented figures; this article contains no current price data.
The bottom line
With gold karats explained, gold content becomes a simple calculation: karat divided by 24. We recommend using that fraction with an accurate weight and a live spot quote to estimate melt value, remembering that higher karat trades durability for purity, and having valuable items tested professionally. This is not financial advice.