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Estimate a piece’s gold value by multiplying its assessed gold weight in grams by its purity fraction and the current local price per gram for pure gold. For example, 18-karat gold has a purity fraction of 18 ÷ 24, or 0.75. The result is a metal-value benchmark—not a guaranteed offer. A buyer’s assessment, deductions and sale terms determine what you actually receive.
The resale-value formula
Estimated metal value = assessed gold weight (g) × purity fraction × current local gold price per gram
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Use the karat number divided by 24 to find the purity fraction. If the item is marked with a fineness number, divide that number by 1,000. Thus, 18K is 18 ÷ 24 = 0.75, while a fineness mark of 750 is 750 ÷ 1,000 = 0.750. The two marks express the same proportion of gold.
The formula estimates the value of the gold content, not the full retail price of the jewellery. It does not add the original making charge, workmanship or design value. Whether a particular buyer will pay extra for a design, brand, gemstone or collectible value is not established by this metal calculation, so do not assume those amounts are included.
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Calculate an estimate step by step
- Read the purity marking. Note the karat or fineness mark, and check whether the item is described as plated, filled, overlay, rolled-gold-plate or vermeil. Those descriptions do not mean the whole item is solid gold.
- Check what the marking means where you are. Hallmark formats and legal requirements vary by country. A mark can help establish purity, but it is not a substitute for checking the relevant local system or having uncertain metal tested.
- Establish the gold weight in grams. A digital jewellery scale can give you an initial total weight. For a piece with stones or mixed materials, do not automatically treat the entire item’s weight as gold weight; ask the buyer what weight it accepts and how it handles non-gold components.
- Find a current local price per gram for pure gold. Use a rate in the currency and market relevant to your sale, and note when it was quoted. Gold prices and currency conversions change. An old example rate is not a current offer.
- Multiply and compare. Multiply accepted weight by the purity fraction and the current price per gram. Then request and compare itemized net offers from more than one buyer.
A household or jewellery scale measures weight; it does not authenticate a purity stamp or determine the proportion of gold in an alloy. If the purity is uncertain, treat the result as an estimate and ask how the buyer verifies it.
Worked example: estimating 18K gold
Suppose a hypothetical piece weighs 10 g, is marked 18K, and the hypothetical local price for pure gold is 50 currency units per gram. These figures are only for showing the arithmetic, not a market quote.
- Purity fraction: 18 ÷ 24 = 0.75.
- Pure-gold-equivalent weight: 10 g × 0.75 = 7.5 g.
- Estimated metal value: 7.5 g × 50 = 375 currency units.
This calculation assumes that all 10 g is the relevant gold alloy weight. If stones or other materials make up part of the total, a buyer may accept a lower gold weight. The buyer’s purity assessment, price basis, fees and other terms can also change the final payment.
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The same method works for other marks. For 14K, the purity fraction is 14 ÷ 24, or about 0.5833; for 9-carat gold marked 375, it is 375 ÷ 1,000, or 0.375. Once you have the accepted weight and the applicable fraction, the remaining step is to multiply by the current local price for pure gold per gram. Keep the inputs visible in your notes so you can spot whether two estimates differ because of purity, weight or price.
Understand karat and fineness marks
Karat
Karat indicates how many parts out of 24 are gold. The U.S. Federal Trade Commission’s consumer explanations use 18K to mean 18 parts gold and 6 parts other metals, and 14K to mean 14 parts gold and 10 parts other metals. To use karat in the formula, divide it by 24: 14K is 14 ÷ 24, or about 0.5833; 18K is 0.75.
Fineness
Fineness expresses the amount of gold in parts per thousand. For example, a 750 mark means 750 parts gold per 1,000, or a purity fraction of 0.750. UK government hallmarking guidance gives 375 as the fineness mark for 9-carat gold: at least 375 parts gold per 1,000. Convert a fineness mark for the formula by dividing it by 1,000.
Plated, filled and similar descriptions
Do not apply the formula to the entire weight of an item described as gold-plated, gold-filled, overlay, rolled-gold-plate or vermeil as if it were solid gold. These terms describe gold applied to another material rather than an item made throughout of a gold alloy. The applied layer’s presence does not establish that the base item’s full weight has the stated gold purity. Ask the buyer whether it accepts the piece and what, if anything, it will count as recoverable gold.
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Check the hallmark for your country
Hallmarking is not one universal system. The World Gold Council notes that national requirements vary, and the marks used in the United Kingdom, United States and India should not be treated as interchangeable. Use the applicable local authority’s guidance to interpret a mark; a familiar-looking number alone may not tell you everything about a piece’s origin or status.
United Kingdom
UK government guidance describes a full hallmark as including a sponsor or maker mark, a fineness mark and an assay office mark. It gives 375 as the fineness mark for 9-carat gold and states a 1 g gold exemption threshold in its hallmarking guidance. These are UK-specific details, not general rules for jewellery sold elsewhere. The government also explains hallmarking as an independent guarantee of precious-metal purity and says hallmarking is legally required for precious-metal items over a certain weight.
India
India’s Bureau of Indian Standards (BIS) hallmarking scheme has its own components, including a traceable HUID. Consult BIS guidance to interpret marks under that scheme; do not assume that another country’s hallmark format has the same meaning.
United States and other jurisdictions
The Federal Trade Commission explains karat and descriptions such as plated and filled, but marking systems and legal requirements differ across jurisdictions. If a stamp is unclear, missing or inconsistent with the seller’s description, check the relevant local authority or ask a reputable buyer how it will verify the item before you rely on the stamp in a calculation.
How much will a jeweller actually pay?
The formula gives you a benchmark for the gold content. A buyer may assess the item’s purity and recoverable gold weight and then quote according to its own terms. The benchmark is therefore not a promise that a buyer will pay that amount, and there is no universal deduction percentage established by the consumer guidance cited here.
Ask each buyer to explain its calculation and show the figures that lead from the item to the net payment. Compare offers for the same piece and the same type of transaction; a cash sale and an exchange may have different terms, so compare like with like.
- Accepted gold weight, including how stones and other materials are treated.
- Assessed purity and how the buyer verified it.
- Price per gram, currency and the time the price was quoted.
- Any assay, refining, handling or other deductions or fees.
- Whether the quote is for a cash sale or an exchange.
- The final net amount you would receive.
Request the terms in writing or in an itemized quote where possible. The BBC Skillswise consumer guide advises comparing offers from more than one buyer; that is more useful than assuming every buyer applies the same rate or deductions.
If one quote looks higher than another, compare the underlying figures rather than only the headline amount. A buyer might be using a different accepted weight, purity assessment, price-per-gram basis, fee or transaction type. Ask the buyer to explain any difference in plain terms. A quote that does not show its inputs is difficult to compare with a second offer, even if both buyers describe it as based on the current gold rate.
Get the weight and price inputs right
Weighing a stone-set or mixed-material item
A scale records the weight of everything placed on it. In a ring with a stone, for example, that total includes the stone as well as the metal. A buyer may use a different accepted gold weight after accounting for non-gold components. Weighing the item at home can help you understand its approximate total mass, but it cannot tell you how much of that mass the buyer will count as gold.
Ask the buyer to state the accepted weight rather than multiplying the full item weight by the purity fraction without qualification. If buyers provide different weights, ask what each included or excluded before comparing their offers.
Using a current local gold rate
Use a price per gram that matches the currency and market in which you are considering the sale. If the rate you find is quoted in U.S. dollars per troy ounce, it is not directly comparable to a local per-gram rate: first establish the appropriate unit and currency conversion, then confirm that the resulting rate is current. The BBC Skillswise guide specifically cautions readers about converting a U.S.-dollar-per-troy-ounce price to a local per-gram figure.
Record the rate and its timestamp when you make your estimate. If a buyer quotes a different rate, ask which price it is using and when that price applies. A rate from an earlier day—or a price for a different unit, currency or market—can make an otherwise correct multiplication misleading.
Do not mix a pure-gold price with a weight or purity figure that has not been adjusted as the formula requires. The formula first reduces the assessed alloy weight to its pure-gold-equivalent amount using the purity fraction; that amount is then multiplied by the price for pure gold. If a buyer provides a price for a different basis, ask it to explain the basis so you do not compare unlike figures.
What to do if you are unsure about purity
A stamp is useful evidence, but an unclear or absent mark may leave you without a reliable purity input. Do not solve that uncertainty by guessing a karat value or by treating the item’s appearance as proof. Ask a reputable buyer or the relevant local assay authority what verification method it uses, what it costs and whether the test affects the item.
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In India, BIS says consumers may submit hallmarked or unhallmarked jewellery to a BIS-recognized Assaying and Hallmarking Centre for chargeable testing and receive an assay report. This is a documented option for consumers in India; availability, fees and procedures elsewhere depend on the relevant local authority or provider.
Before agreeing to a test or sale, clarify whether the buyer is assessing the item for a quote or whether you are commissioning a separate assay. Ask whether there is a charge, what result or report you will receive, and whether any testing procedure could affect the jewellery. The details depend on the provider, so confirm them directly rather than assuming every test follows the same process.
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- Write down each item’s markings and approximate total weight. Separate pieces rather than combining them, since their purity or construction may differ.
- Ask each buyer to assess the same item and give its accepted gold weight and purity.
- Record the buyer’s price per gram, currency and timestamp, along with any deductions or fees.
- Check whether the offer is for cash or an exchange, and note the final net payment—not just a headline price or metal-rate figure.
- Compare the itemized offers and ask about any unexplained difference before accepting one.
This process makes clear whether an apparent difference comes from the assessed weight, purity, price basis, deductions or transaction terms. It also keeps the estimate distinct from the actual amount the buyer commits to pay.
A simple comparison note can be enough: list the item, its marks and total home weight, then make a row for each buyer’s accepted weight, assessed purity, quoted rate and time, fees, sale or exchange terms, and net payment. This does not replace the buyer’s assessment; it helps you check that you are comparing the same piece on the same basis. If a quote leaves a line blank, ask for clarification before treating it as comparable.
Keep separate estimates for different pieces, especially if they carry different marks or include stones and other materials. Combining everything into one total can hide the reason for a lower or higher offer. The point is not to predict a universal payout, but to understand each buyer’s calculation and decide whether the stated terms suit you.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Common calculation mistakes
- Using the karat as a whole-number multiplier: 18K does not mean 18 times the gold price. Convert it to 18 ÷ 24 = 0.75 first.
- Confusing fineness with karat: divide a fineness mark such as 750 by 1,000, not by 24.
- Counting the full weight of a plated item as gold: the description indicates an applied layer, not a solid-gold item throughout.
- Assuming total jewellery weight equals accepted gold weight: stones and other materials may affect what the buyer counts.
- Using an outdated or mismatched gold rate: confirm the date, currency and unit, particularly if converting a troy-ounce quote to a local per-gram price.
- Treating the estimate as a guaranteed payout: buyer assessment and terms determine the final net offer.
- Adding the original retail or making cost to the metal calculation: the formula values gold content and does not establish that workmanship, design or making charges will be recovered.
Frequently Asked Questions
How much is my gold jewellery worth?
For a rough metal-value estimate, multiply the buyer-assessed gold weight in grams by the purity fraction and a current local price per gram for pure gold. This estimates the metal content, not a guaranteed offer. The buyer’s assessment, deductions and sale terms determine the net payment.
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Divide 18 by 24 to get a purity fraction of 0.75. Multiply the accepted weight of the gold alloy by 0.75, then multiply that pure-gold-equivalent weight by the current local price per gram for pure gold. For instance, 10 g of relevant 18K alloy is equivalent to 7.5 g of pure gold for this estimate.
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What will a jeweller pay for my old gold?
There is no single guaranteed payout. A buyer may assess purity and recoverable gold weight, apply its quoted price basis and deduct fees or other amounts under its terms. Ask for the weight, purity, price per gram, timestamp, deductions and final net payment, then compare more than one buyer’s itemized offer.
Does a hallmark guarantee the resale price?
No. A hallmark can provide evidence of precious-metal purity, but hallmark formats and requirements vary by country. It does not set the buyer’s price or guarantee the final offer. If a mark is unclear or absent, ask a reputable buyer or local assay authority about verification.
Can I use the full weight of a ring with a stone in the calculation?
Not automatically. A home scale gives the total weight of the ring, including the stone and other non-gold components. Ask the buyer what accepted gold weight it uses and compare that figure across quotes.
Are making charges and design costs included in the estimate?
No. The formula estimates the value of the gold content and does not add the original making charge, workmanship or design value. Do not assume those costs are recoverable in a resale offer.
Can gold jewellery with no hallmark be tested?
In India, BIS says consumers can submit hallmarked or unhallmarked jewellery to a BIS-recognized Assaying and Hallmarking Centre for chargeable testing and receive an assay report. Elsewhere, check with the relevant local assay authority or a reputable buyer about the method, fee and result.
The Bottom Line
To estimate gold jewellery’s metal value, use the accepted gold weight in grams × the purity fraction × a current local price per gram for pure gold. Treat the result as a benchmark, not a promised payout: confirm how the buyer assessed weight and purity, ask for itemized deductions and net terms, and compare more than one offer.
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