When you hear the term “gold bar,” you may picture a brick made out of gold. However, the truth is, most gold bars are significantly smaller than this. Due to the high value of gold, even a small gold bar can be worth quite a bit.

A gold bar is a standard quantity of pure gold that has been minted or stamped into a brick-like shape. When investing in gold bars, there are many different size options from which to choose, ranging from the tiny one gram to the massive 400-troy-ounce bar. Which size to purchase depends on your needs as an investor.

Ounces or Grams

Gold is usually measured in troy ounces, equivalent to approximately 31.1 grams. Some gold bars are measured in ounces, while others are measured in grams. When referring to gold bars, it is important to note that the ounce weight refers to a troy ounce, rather than a avoirdupois ounce (the ounce generally encountered in daily life), which is lighter than a troy ounce.

Buying in Bulk vs. Divisibility

The largest bars carry the smallest per-ounce premium. As such, you will find the lowest per-ounce prices when buying the largest gold bars you can afford. However, there are downsides to this investing strategy.

If you only invest in large gold bars, you can only buy or sell quantities as small as one large bar. Smaller bars, meanwhile, offer the option to buy or sell smaller quantities at a time. For investors who purchase gold as a hedge against the possibility of an economic collapse, and plan to use their gold bars as a form of currency, this is an important consideration. Investors more commonly purchase 1-ounce or 10-ounce gold bar sizes, or those in even smaller sizes such as 1 to 500 grams.

Common Sizes

The standard gold brick, held as gold reserves by central banks, is the 400-troy-ounce bar. Known as the Good Delivery Bar, it weighs approximately 12.4 kilograms (438.9 ounces). The largest gold bar typically used for trading and investment purchases is the kilo bar (1000 grams or 32.15 troy ounces). At this size, the gold bar is more affordable, and carries a low premium over the spot value of the gold, making it ideal for transfers between banks and investors.

Gold bars are commonly made in a range of smaller sizes. These include 20, 10, 5, 1, or one-half troy ounce, as well as 500, 250, 100, 50, 20, 10, 5, or 1 gram. Common gold bar sizes also include one tola (11.66 grams), ten tola (117 grams or 3.75 troy oz), and one tael (50 grams). The Tola is a traditional Indian measure for gold weights that continues to be used by international gold manufacturers to this day.

The dimensions of any particular gold bar weight vary significantly from one mint to another. Because gold is a relatively dense material, gold bars are relatively small for their weight. A one ounce bar is approximately 1.75 inches long, 1 inch wide, and less than a tenth of an inch thick. Typical measurements, in centimeters, are 20x8x4.5 for the 400 ounce bar, 8x4x1.8 for the 1 kilo bar, and 5.5x.31×0.3 for the 100 gram bar. The smallest commonly-produced gold bar, weighing 1 gram, measures just 15mm x 8mm x 0.4mm.