Ounces and grams are two common units used to measure weights in small quantities. Ounces commonly are used in the United States, where the main unit of measurement for weights is the pound. An ounce is 1/16 of a pound. Grams are the main base of measurement for weights in the metric system, which is used in many countries, including all of continental Europe. A simple calculation will easily convert weights in ounces to grams.

Measurements sometimes are in fluid ounces, which are not equivalent to ounces. Fluid ounces are a measure of volume, with eight fluid ounces equaling one cup. Some substances such as butter weigh almost exactly one ounce per fluid ounce of volume, but many others are quite different. To convert fluid ounces to ounces, you will need to look up the density of the specific item being measured.

Determine the kind of ounces. In most cases, the weight is referring to the avoirdupois ounce. However, precious metals are measured in the troy ounce, which weighs slightly more than the avoirdupois ounce. Unless troy ounces are specified or the item is gold, silver or a gemstone, it is usually safe to assume the item is measured in avoirdupois ounces.

Multiply the number of ounces by 28.35 to determine the weight in grams. For a more exact calculation, multiply by 28.34952313.

Multiply the number of troy ounces by 31.1 to convert the weight in grams. For a more exact calculation, as may be required for precious metals and gemstones, multiply by 31.1034768.

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