18 Karat Gold Price per Gram: How to Calculate It
By Maxence Roux· Published on · Updated on
Do you have an 18 karat gold ring, chain or bracelet and want to know its value? Good news: the calculation is simple. You only need three pieces of information: the object's weight, its fineness and the gold price. This guide explains the method step by step, with examples.
Do you have an 18 karat gold ring, chain or bracelet and want to know its value? Good news: the calculation is simple. You only need three pieces of information: the object's weight, its fineness and the gold price. This guide explains the method step by step, with examples.
Indicative values and examples only. This content is for information and does not constitute investment advice.
What does “18 karat” mean?
Karat measures the proportion of pure gold in an alloy on a scale of 24. 24 karat gold is (almost) pure gold. 18 karat gold contains 18 parts pure gold out of 24, or 75%. The remaining 25% consists of other metals, such as copper or silver, which make the jewelry stronger and give it its color (yellow, rose or white gold).
This proportion is also expressed in thousandths: 18 karat gold has a fineness of “750 parts per thousand,” or “750 ‰”.
Karat conversion table
| Karats | Proportion of pure gold | Fineness in thousandths |
|---|---|---|
| 24 karat | 99.9% | 999 ‰ |
| 22 karat | 91.7% | 916 ‰ |
| 18 karat | 75% | 750 ‰ |
| 14 karat | 58.5% | 585 ‰ |
| 9 karat | 37.5% | 375 ‰ |
Unsure which fineness to choose? Read our 14 karat vs 18 karat gold comparison.
The formula for calculating the value of 18 karat gold
The metal value of a gold object is calculated as follows:
Metal value = object's weight (in grams) × fineness ÷ 1,000 × pure gold price per gram
For 18 karat gold, the fineness is 750. The formula therefore becomes:
Metal value = weight × 0.75 × pure gold price per gram
Worked example
Take an 18 karat gold chain weighing 10 grams and a hypothetical price of $100 per gram of pure gold (this figure is only an example and does not represent today's price).
- Pure gold weight: 10 g × 0.75 = 7.5 g
- Metal value: 7.5 g × $100 = $750
Your chain therefore contains 7.5 grams of pure gold, with an indicative metal value of $750 using this example price.
For a result using real prices, updated throughout the day, use our gold calculator or check the metal prices.
Pay attention to the actual gold weight
The weight shown on your scale is not always the actual gold weight. Remember to exclude:
- precious or imitation stones, which can weigh a significant amount;
- clasps, springs or steel parts, sometimes found in bracelets and watches;
- components made of another metal, such as a silver setting.
For jewelry set with stones, only a professional can precisely estimate the gold weight after disassembly.
Metal value, buyback price and retail price: three different amounts
The most common mistake is to assume that jewelry can be resold for its metal value.
- Metal value is the theoretical value of the pure gold contained in the object, calculated using the formula above.
- The buyback price is what a professional actually offers you. It is generally lower than the metal value because it includes melting and refining costs and the buyer's margin.
- The jewelry retail price is often much higher than the metal value because it includes craftsmanship, design, brand and the store's margin.
Knowing the metal value therefore mainly helps you compare buyback offers and avoid an offer that is too low.
How can you recognize 18 karat gold?
Look for international fineness marks such as “750” or “18K”, and “585” or “14K”. Hallmark systems differ by country. The eagle's head is an official French hallmark example, not a universal mark. If in doubt, have a jeweler or assayer check the object. See our hallmark guide.
Common mistakes to avoid
- Confusing gold karats with diamond carats: for a diamond, a carat is a unit of weight (0.2 g), unrelated to gold purity.
- Using the price per ounce without converting it: a troy ounce is approximately 31.1 grams. Divide the price per ounce by 31.1035 to obtain the price per gram.
- Forgetting the currency: prices are often quoted in US dollars. Check the currency before calculating.
- Weighing with a kitchen scale: prefer a precision scale accurate to one hundredth of a gram.
Track the value of your jewelry with Metalstat
Instead of repeating the calculation every time, record your jewelry, coins and bars in Metalstat. Enter each object's weight and fineness: Metalstat automatically calculates its indicative metal value using real prices, updated throughout the day and tracks your collection's evolution over time.
Notes for readers worldwide
Examples use US dollars. The formulas work in any currency, provided purchase costs, metal quotes, and sale proceeds use the same currency. Metalstat lets you display values in USD, EUR, MAD, GBP, or CHF; not every currency is available in the app.
Gold prices are often quoted per troy ounce. One troy ounce is approximately 31.1035 g: divide the price per troy ounce by 31.1035 to obtain the price per gram, then apply fineness and quantity. Do not use an ordinary ounce.
Gold purity is expressed in karats (K). 14K is common in the United States, 18K is widely used in Europe, and 22K–24K is popular in parts of Asia and the Middle East; practices vary by market and product. International marks include “750” or “18K” and “585” or “14K”. An eagle's head is a French hallmark example, not a worldwide requirement, and a mark alone does not prove authenticity.
Tax, identification, payment, and selling rules vary by country and, in the United States, by state. Check with your local tax administration and other relevant authorities, or consult a qualified local professional. Do not assume a rule from another country applies to your sale.
Frequently asked questions
How much is 1 gram of 18 karat gold worth? One gram of 18 karat gold contains 0.75 grams of pure gold. Its metal value therefore equals 75% of the pure gold price per gram. With a hypothetical price of $100 per gram, 1 gram of 18 karat gold has a metal value of $75.
Is 18 karat gold real gold? Yes. 18 karat gold contains 75% pure gold. It offers a balance between purity and strength; commonly used karats vary by country.
Why does a jeweler offer me less than the metal value? The buyback price takes into account melting and refining costs, the professional's margin and sometimes the difficulty of assessing the object. Compare several offers before selling.
What is the difference between yellow, rose and white 18 karat gold? They contain the same proportion of pure gold (75%). Only the other metals in the alloy differ, changing the color. Their metal value is therefore the same at equal weight.
Where can I find the gold price per gram? You can check real indicative prices, updated throughout the day on our metal prices page, along with its source, date and currency.
In summary
To calculate the value of 18 karat gold, multiply the actual gold weight by 0.75, then by the pure gold price per gram. Remember that this metal value is an estimate: the buyback price offered by a professional will generally be lower. To easily track your jewelry's value, try Metalstat for free.
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