Step 1: establish the net metal weight
Start with weight in grams. Gross jewellery weight includes everything on the scale: gold alloy, stones, enamel and any non-gold fittings. An estimate based on gross weight may overstate the gold value when these components are substantial.
An invoice may distinguish metal weight and stone weight, but old paperwork is not a substitute for checking the actual piece. Ask a professional to explain exclusions and record the measured net weight. Do not dismantle a valuable or sentimental item yourself.
Step 2: understand the purity basis
Karat is a proportion out of 24. Nominal 18K alloy is 75% gold; a 750 fineness mark expresses the same proportion in parts per thousand. For common 22K jewellery, a 916 mark indicates 91.6% fineness. Use the tested or appropriately documented purity rather than a guess from colour.
If the selected rate is for pure gold, an indicative gold-content estimate uses the purity fraction. If the selected rate already applies to the jewellery’s karat, multiplying by purity again would understate the estimate. Know which kind of rate you have.
Step 3: use a consistent rate and unit
A general gold-content estimate is net alloy weight × gold purity fraction × reference price per gram of pure gold. This explains metal content only; it is not CMG’s internal purchasing formula or a commitment to pay that amount.
Convert a per-10-gram price into a per-gram price before using it. Avoid mixing a buying quote with a retail rate or combining amounts from different dates without recognising the limitations. Know My Gold offers an easier way to explore an indicative result.
Worked example — illustrative numbers only
Assume a piece weighs 12 grams in total, including 2 grams of non-gold components. Its net alloy weight is therefore 10 grams. Assume the alloy is 18K, or 75% gold, and use an imaginary pure-gold reference price of ₹8,000 per gram. This is an illustrative price, not today’s rate or a CMG offer.
The estimated gold content is 10 × 0.75 = 7.5 grams. The illustrative metal-content value is 7.5 × ₹8,000 = ₹60,000. Using the gross 12 gram weight would give ₹72,000 and incorrectly treat the non-gold components as gold.
If ₹6,000 per gram were already an illustrative 18K rate, the calculation would instead be 10 × ₹6,000 = ₹60,000. Do not multiply that amount by 0.75 again. The example shows why the rate basis matters as much as the arithmetic.
Why a final offer can differ
A calculator cannot inspect solder, plating, mixed-purity parts or stone weight. Meenakari and other decorative materials also complicate the relationship between gross weight and net metal content. The measured item may not match the assumptions entered.
A final purchase quote considers verified weight and purity, the applicable buying rate and the buyer’s stated assessment terms. Ask for the full explanation of proposed adjustments. Keep the indicative number as a comparison aid, not an entitlement or guaranteed payout.