Gold Weight Calculator - Troy Ounce, Pennyweight, Karat Purity

A gold weight calculator turns a single entered value, in any unit a jeweler, refiner, or stacker actually uses, into the same mass expressed in every other gold unit plus the pure 24-karat gold content of the piece. Pick troy ounces, grams, pennyweights, grains, kilograms, avoirdupois ounces, or pounds, then choose a 9K to 24K karat preset. The same fixed unit-conversion factor is used by the London Bullion Market Association, so a 1 troy ounce input gives 31.1035 grams regardless of which karat is picked, and a karat below 24 splits off the fine gold mass at the published purity ratio.

• • Jewelry and Scrap Gold Payouts: Jewelers and refiner intake counters quote a payout from a pennyweight or gram scale reading.
• • Coin and Bar Inventory Counts: Stackers and dealers weigh coins or small bars on a kitchen scale to read off troy-ounce and gram totals.
• • Coursework and Metallurgy Problems: Physics students check the gold unit conversion and karat-to-percentage ratio for homework.
• • Bullion Reference Masses: Reference 1 g, 1 oz, 100 g, 1 kg, and the 350 to 430 troy ounce LBMA Good Delivery bar.

Gold is unusual among common metals because the trade uses the troy ounce, the apothecary grain, and the pennyweight rather than the everyday ounce, gram, and kilogram, so a piece of jewelry weighed on a gram scale needs the right conversion factor before the karat ratio is applied. The result is independent of the gold spot price.

For a copper or brass object, the same density-times-area-times-length pattern shows up in the copper wire weight calculator.

The calculator converts the entered value into grams using a fixed unit factor, then multiplies that gross mass by the karat ratio to get the fine (pure 24-karat) gold content. Both values are re-expressed in every supported gold unit.

• value: Numeric weight in the chosen input unit. Any non-negative real number, with zero allowed.
• inputUnit: Unit of the entered value. Troy ounces, grams, kilograms, pennyweights, grains, avoirdupois ounces, or avoirdupois pounds.
• karat: Karat preset (9K to 24K) or 'custom' for an arbitrary purity entered as a percentage.
• customPurityPct: Custom gold purity as a percentage of pure gold. Used only when the karat preset is 'custom'.

The gram factor for every gold unit is fixed by the international troy ounce convention used by the London Bullion Market Association for Good Delivery bars, with 24K treated as the pure gold reference and 18K equal to 75.0 percent pure. The custom purity field covers millesimal bars and refined grain; a 99.95 percent purity, the LBMA Good Delivery minimum, gives a fine gold content about 0.05 percent below the gross mass.

According to London Bullion Market Association, one troy ounce equals exactly 31.1034768 grams, 20 pennyweights equal one troy ounce, and a Good Delivery bar weighs 350 to 430 fine troy ounces (about 12.4 kg).

When the result needs to move into non-gold mass units like pounds, milligrams, or stones, the weight converter applies the same SI and customary factors across the full mass table.

Four ideas show up in every gold mass problem. Once these are clear, the formula and the result panel both make sense.

The troy weight system divides cleanly into 12 and 240; the avoirdupois ounce divides into 16 of a pound, which is more convenient for groceries and postage but inconvenient for precious metals. Karat and fineness are two ways to say the same thing, so 24K equals 999 fineness and 18K equals 750 fineness.

The 9.7 percent gap between a troy ounce and an everyday ounce is the same kind of trap the ounce to kg converter catches by making the unit explicit on both sides of the conversion.

Five steps take you from a weighed piece of gold to a clean result in every gold unit and the fine gold content.

1. 1 Pick the Unit of the Scale Reading: Use troy oz for coin and bar measurements, gram for jewelry scales, pennyweight for jeweler scrap, grain for very small items, and ounce or pound for kitchen scales.
2. 2 Enter the Gold Weight: Type the number from the scale. Use 0 to clear the result panel.
3. 3 Pick the Karat Preset: Match the karat stamp on the jewelry or bar. Custom opens the purity field for millesimal bars and refined grain.
4. 4 Enter Custom Purity if Needed: Type the millesimal fineness divided by 10 (for example, 99.95 for 999.5 fineness, 75.0 for 750 fineness).
5. 5 Read the Gross and Fine Gold Weights: Gross is total mass in grams; fine is the pure 24K portion. Use fine grams for melt work and gross grams for shipping.

A 12.4 g piece of 18K jewelry on a gram scale returns 0.3987 troy ounces total and 0.2990 troy ounces of fine gold.

When the same number is needed in kilograms and avoirdupois ounces, the kg to ounce converter applies the same NIST factors without a karat step.

The calculator handles the two pieces of information a gold user actually needs, the same mass in every gold unit and the pure gold content, in one step.

• • Covers Every Gold Unit: Shows the same mass in troy ounces, grams, kilograms, pennyweights, grains, avoirdupois ounces, and pounds.
• • Applies the Karat Ratio in One Pass: Picks 9K to 24K or a custom purity and reports the fine gold content automatically.
• • Bidirectional: Enter 1 troy ounce and get 31.1035 g, or enter 31.1035 g and get 1.0000 troy ounce.
• • Bullion Reference Values: Presets match 1 g, 1 troy oz, 100 g, 1 kg, and the 400 troy oz Good Delivery bar for cross-checking dealer listings.
• • Independent of Spot Price: Returns mass only, so the result is stable when the gold spot price moves.

The karat ratio is the only place where alloy type enters the formula, so switching from 18K to 14K only changes the fine gold content; the gross weight, troy ounces, and gram totals stay the same. For a buyer or refiner, the most useful output is fine gold content in grams; for a stacker, the most useful output is the troy ounce total.

When the scale reads pounds and ounces rather than grams, the pounds and ounces calculator breaks the avoirdupois pound into the same ounces this calculator already supports.

Five factors shift the result, plus two limitations to keep in mind when comparing the calculator to a real assay sheet.

• • The result assumes the entered karat or purity is accurate. Stamps can be off, especially on lower-karat alloys, so an independent assay is the only way to confirm fine gold content for a payout.
• • The calculator does not include the gold spot price. For a payout, multiply the fine gold grams by the current price per gram from a separate gold price or melt calculator.

Most of the day-to-day variation in a result comes from the karat preset rather than from the unit conversion. A coin, bar, or piece of jewelry measured in troy ounces, grams, or pennyweights should agree to within 0.1 percent, and any larger gap is a scale calibration or unit mistake rather than a calculator error. The custom purity field is the most important factor for refined grain and small bars; a 99.99 percent pure 1 g bar is essentially the same as 24K for fine gold content.

According to World Gold Council, the karat system measures gold purity in parts per 24, so 24-karat is the highest standard purity, 18-karat is 75.0 percent pure, 14-karat is 58.3 percent pure, and 10-karat is 41.7 percent pure.

When the same piece needs a volume figure for casting, melt sizing, or freight, the volume to mass calculator applies the 19320 kg/m^3 gold density preset to return cubic centimeters for the same piece.