Gram

For other uses of the words gram or gramme, see gram (disambiguation).

The gram or gramme (Greek/Latin root grámma); symbol g, is a unit of mass.

Originally defined as "the absolute weight of a volume of pure water equal to the cube of the hundredth part of a metre, and at the temperature of melting ice"^[1] (later 4 °C), a gram is now defined as one one-thousandth of the SI base unit, the kilogram, or 1×10⁻³ kg, which itself is defined as being equal to the mass of a physical prototype preserved by the International Bureau of Weights and Measures.

Additional recommended knowledge

Weighing the right way

Essential Laboratory Skills Guide

How to ensure accurate weighing results every day?

Examples

All masses are approximate:

• Plastic pen cap (Bic): 1 gram
• A single Smartie: 1 gram
• Paper clip: 0.5 grams to 1.5 grams
• 1 US banknote (any denomination): 1 gram^[2]
• 1 Litre of air: 1.2 grams
• A teaspoon of salt: 4.745 grams
• Typical sheet of A4 paper: 5 grams
• United States nickel: 5 grams (very accurate when new)^[3]

Other abbreviations

The International System of Units abbreviation for the gram is g, and follows the numeric value with a space, as in "200 g"^[4][5]. In some fields and regions, the international standard symbols for units are used quite strictly, in particular in technical and scientific publications and in legally regulated product labels. In other contexts (e.g., grocery market traders), a wide range of other abbreviations can also be encountered, such as gr, gm, grm, gms, grms.

History

It was the base unit of mass in the original French metric system and the later centimetre-gram-second (CGS) system of units. The word originates from late Latin gramma – a small weight.

Uses

The gram is today the most widely used unit of measurement for non-liquid ingredients in cooking and grocery shopping worldwide. For food products that are typically sold in quantities far less than 1 kg, the unit price is normally given per 100 g.

Most standards and legal requirements for nutrition labels on food products require relative contents to be stated per 100 g of the product, such that the resulting figure can also be read as a percentage.

Conversion factors

• 1 grain = 0.06479891 gram
• 1 ounce (avoirdupois) = 28.349523125 grams
• 1 ounce (troy) = 31.1034768 grams

References

1. ^ Décret relatif aux poids et aux mesures, 1795
2. ^ [1]
3. ^ [2]
4. ^ SI brochure, Section 3.2
5. ^ NIST Special Publication 811

See also

• Conversion of units
• Gold gram