Convert Ounces to Kilograms

Ounce - The ounce (abbreviated: oz, the old Italian word onza, now spelled oncia;) is a unit of mass in a number of different systems, including various systems of mass that form part of the imperial and United States customary systems. Its size can vary from system to system. The most commonly used ounces today are the international avoirdupois ounce and the international troy ounce.

Historically, in different parts of the world, at different points in time, and for different applications, the ounce (or its translation) has referred to broadly similar but different standards of mass (or weight, before the distinction between weight and mass developed). An ounce is more often a measure of force as opposed to mass or weight, comparable to lbf, or pound force.

International avoirdupois ounce - The avoirdupois ounce is the most commonly used ounce today. It is defined to be one sixteenth of an avoirdupois pound. It is therefore equal to 437.5 grains. In 1958 the United States and countries of the Commonwealth of Nations agreed to define the international avoirdupois pound to be exactly 0.45359237 kilograms. Consequently, since 1958, the international avoirdupois ounce is exactly 28.349523125 grams by definition. The ounce is commonly used as a unit of mass in the United States. On January 1, 2000 it ceased to be a legal unit of measure within the United Kingdom for economic, health, safety or administrative purposes but remains a familiar unit, especially amongst older people.

International troy ounce - A troy ounce (abbreviated as t oz) is equal to 480 grains. Consequently, the international troy ounce is equal to exactly 31.1034768 grams. There are 12 troy ounces in the now obsolete troy pound. Today, the troy ounce is used only to express the mass of precious metals such as gold, platinum, palladium or silver. For historical measurement of gold, a fine ounce is a troy ounce of 99.5% (".995") pure gold, a standard ounce is a troy ounce of 22 carat gold, 91.66% pure (11 "fine ounces" plus one ounce of alloy material), in modern day, an ounce of gold (1 troy ounce) is referred as a 99.99% pure gold piece or gold grains (gold shot).

Apothecaries' ounce - The obsolete apothecaries' ounce equivalent to the troy ounce, was formerly used by apothecaries (now called pharmacists or chemists).

Maria Theresa ounce - "Maria Theresa ounce" was once introduced in Ethiopia and some European countries, which was equal to the weight of one Maria Theresa thaler, or 28.0668 g. Both the weight and the value are the definition of one "Birr", still in use in present-day Ethiopia and formerly in Eritrea.

Metric ounces - Some countries have redefined their ounces to fit in with the metric system. The Dutch have redefined their ounce (in Dutch, ons) as 100 grams. The Dutch's metric values, such as 1 ons = 100 grams, is inherited, adopted and taught in Indonesia since elementary school. It is also formally written in Indonesian national dictionary (Kamus Besar Bahasa Indonesia) and elementary school's formal manual book. East Asia has a traditional ounce, known as a tael, of varying value. In China, it has been given a metric value of 50 grams.

Kilogram - The kilogram or kilogramme (symbol: kg) is the base unit of mass in the International System of Units (SI, from the French Le Systeme International d'Unites). The kilogram is defined as being equal to the mass of the International Prototype Kilogram (IPK), which is almost exactly equal to the mass of one liter of water. It is the only SI base unit with an SI prefix as part of its name. It is also the only SI unit that is still defined in relation to an artifact rather than to a fundamental physical property that can be reproduced in different laboratories.

In everyday usage, the mass of an object, which is measured in kilograms, is often referred to as its weight. However, the term weight in strict scientific contexts refers to the gravitational force of an object. Throughout most of the world, force is measured with the SI unit newton and the non-SI unit kilogram-force. Similarly, the avoirdupois (or international) pound, used in both the Imperial system and U.S. customary units, is a unit of mass and its related unit of force is the pound-force. The avoirdupois pound is defined as exactly 0.45359237 kg, making one kilogram approximately equal to 2.2046 avoirdupois pounds.

Many units in the SI system are defined relative to the kilogram so its stability is important. After the International Prototype Kilogram had been found to vary in mass over time, the International Committee for Weights and Measures (known also by its French-language initials CIPM) recommended in 2005 that the kilogram be redefined in terms of a fundamental constant of nature. No final decision is expected before 2011.