How heavy is a gold bar?

The bar people picture in a bank vault is the London Good Delivery bar, the standard used by the London bullion market and by central banks. Its nominal weight is 400 troy ounces, and 400 × 31.1035 g comes to 12.44 kg (27.4 lb). The rules of the London Bullion Market Association (LBMA) allow anything from 350 to 430 fine troy ounces, so a real bar can weigh 10.9 to 13.4 kg. The LBMA says typical bars land a few ounces either side of 400.

The 400 ounces counts the gold, not the whole bar. A Good Delivery bar must be at least 995 parts per thousand gold, so a bar holding 400 ounces of gold weighs about 402 ounces in total, roughly 12.5 kg. Each bar is weighed on delivery and its gross weight recorded in steps of 0.025 troy ounce, rounded down. The weight is not stamped on the bar; the stamps are the serial number, refiner’s mark, fineness and year.

Vault totals match this. The Federal Reserve Bank of New York reported about 507,000 bars weighing 6,331 tonnes in 2024, an average of about 12.5 kg (27.5 lb) per bar. The Bank of England, the second-largest gold custodian, keeps about 400,000 bars in nine underground vaults.

Gold is weighed in troy ounces. One troy ounce is 31.1 g, about 10% more than the everyday (avoirdupois) ounce of 28.35 g. So 400 troy ounces equals about 439 ordinary ounces, or 27.4 lb.

If a gold bar held 400 ordinary ounces it would weigh exactly 25 lb (11.3 kg). The troy pound works the other way: it has only 12 troy ounces and is lighter than a normal pound.

Gold has a density of about 19.3 g/cm³, so 12.44 kg of it fills only about 645 cm³ (12,440 ÷ 19.3), roughly two-thirds of a litre. The LBMA’s recommended size is a trapezoid about 250 mm long and 70 mm wide across the top and 35 mm high, close to 10 by 2.75 by 1.4 inches.

The bars at Fort Knox are described as about 7 inches long, 3.5 inches wide and 1.75 inches thick, each with about 400 troy ounces of pure gold. Many of them are “coin bars” melted down from old gold coins, which are only about 90% gold. A coin bar therefore weighs more than the gold it contains.

The 400-ounce bar is a wholesale product. Smaller cast bars are common too, especially the 1 kg kilobar (32.15 troy ounces, 2.2 lb) and the 100-ounce bar (3.11 kg, 6.9 lb), and in minted bars down to a single troy ounce.

The largest gold bar ever made weighs 300.12 kg (661.65 lb), about 24 standard bars. Emirates Minting Factory cast it in Dubai in November 2024 at 999.9 purity, and Guinness World Records says it beat the previous record, set by Mitsubishi Materials in Japan in 2005, by 50 kg.