Gold Purity Calculator

This gold purity calculator estimates how much pure gold is inside a gold item and what that metal could be worth using a price you enter manually.

It supports karat-based purity, percentage purity, grams, troy ounces, and kilograms. The calculator converts the gross weight to grams, applies purity, estimates pure gold weight, and then applies your entered price per pure gram.

Use it for early scrap gold, jewellery, coin, or mixed-karat value checks when purity matters. It does not fetch live gold prices, authenticate items, assay metal, quote dealers, convert currencies, or calculate tax.

An 18 karat item is treated as 18 parts gold out of 24, or 75% gold by weight. A 25 gram item at 18 karat contains about 18.75 grams of pure gold before any testing or weighing uncertainty.

If the entered price per pure gram is GBP 58, the simple melt value is GBP 1,087.50. If a dealer pays 92% of that and testing or selling fees are GBP 10, the estimated net value is about GBP 990.50.

Karat expresses purity out of 24. For example, 24k is treated as 100%, 22k as about 91.7%, 18k as 75%, 14k as about 58.3%, and 9k as 37.5%. Percentage mode is useful when a hallmark, assay, or supplier note gives purity directly.

The calculator estimates metal content from the numbers you provide. Real items can include stones, plating, solder, dirt, hollow sections, or mixed metals that change the payable weight.

The price per pure gram is manual. You can enter a spot-derived value, a dealer quote, or your own conservative planning number. The calculator will not look up current prices.

Dealer payable percentage lets you model a buyer paying less than the simple melt value because of spread, refining margin, testing cost, or handling risk. Fees are then subtracted from the payable value.

For a buy-sell return on a known gold holding, use the gold investment calculator. For a general investment gain calculation, use investment return.

This calculator does not verify hallmarks, assay purity, detect plating, weigh stones separately, appraise collectable coins, or replace a professional valuation.

Confirm weight, purity, dealer spread, quote date, currency, fees, and item condition before selling or insuring any gold item.