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Troy weight is a system of units of mass
Mass

In physical science, mass refers to the degree of acceleration a body acquires when subject to a force: bodies with greater mass are accelerated less by the same force....
 customarily used for precious metal
Precious metal

A precious metal is a rare metallic chemical element of high economics value. Chemically, the precious metals are less reactivity than most elements, have high lustre , are softer or more ductility, and have higher melting points than other metals....
s, black powder, and gemstone
Gemstone

A gemstone or gem, also called a precious or semi-precious stone, is a piece of attractive mineral, which — when cut and polished — is used to make jewellery or other adornments....
s.

Named after Troyes
Troyes

Troyes is a communes of France, the Prefectures in France of the northeastern Aube departments of France in France and is located on the Seine river....
, France, the troy system of weights was known to exist in medieval times, at the celebrated fair at Troyes in North Eastern France. One cubic inch
Cubic inch

A cubic inch is a non-International System of Units Units of measurement of volume, equal to the volume of a cube with sides of one inch.Cubic inches are still sometimes used as a unit of measurement in the United States and Canada, although SI is continuing to gradually displace non-SI usage....
 of distilled water, at 62 °F
Fahrenheit

Fahrenheit is a temperature scale named after the physicist Daniel Gabriel Fahrenheit , who proposed it in 1724. Today, the scale has largely been replaced by the Celsius scale; it is still in use for non-scientific purposes in the United States and a few other countries such as Belize....
 (17 °C
Celsius

Celsius is a temperature scale that is named after the Swedish astronomer Anders Celsius , who developed a similar temperature scale two years before his death....
), and at a barometric pressure of 30 inches of mercury
Inch of mercury

Inches of mercury, inHg or "Hg is a measuring unit for pressure. It is still widely used for barometric pressure in weather reports and aviation in the United States, but is considered somewhat outdated elsewhere....
, was determined to weigh 252.458 troy grain
Grain (measure)

In many cultures, a grain is a Physical unit of measurement of mass that is based upon the mass of a single seed of a typical cereal. Historically, in Europe, the average masses of wheat and barley grain were used to define units of mass....
s (gr).

troy ounce (ozt) is 480 grains, somewhat heavier than an avoirdupois
Avoirdupois

The avoirdupois system is a system of Units of measurement based on a pound of sixteen ounces. It is the everyday system of weight used in the United States....
 ounce (437.5 grains).






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Troy weight is a system of units of mass
Mass

In physical science, mass refers to the degree of acceleration a body acquires when subject to a force: bodies with greater mass are accelerated less by the same force....
 customarily used for precious metal
Precious metal

A precious metal is a rare metallic chemical element of high economics value. Chemically, the precious metals are less reactivity than most elements, have high lustre , are softer or more ductility, and have higher melting points than other metals....
s, black powder, and gemstone
Gemstone

A gemstone or gem, also called a precious or semi-precious stone, is a piece of attractive mineral, which — when cut and polished — is used to make jewellery or other adornments....
s.

Named after Troyes
Troyes

Troyes is a communes of France, the Prefectures in France of the northeastern Aube departments of France in France and is located on the Seine river....
, France, the troy system of weights was known to exist in medieval times, at the celebrated fair at Troyes in North Eastern France. One cubic inch
Cubic inch

A cubic inch is a non-International System of Units Units of measurement of volume, equal to the volume of a cube with sides of one inch.Cubic inches are still sometimes used as a unit of measurement in the United States and Canada, although SI is continuing to gradually displace non-SI usage....
 of distilled water, at 62 °F
Fahrenheit

Fahrenheit is a temperature scale named after the physicist Daniel Gabriel Fahrenheit , who proposed it in 1724. Today, the scale has largely been replaced by the Celsius scale; it is still in use for non-scientific purposes in the United States and a few other countries such as Belize....
 (17 °C
Celsius

Celsius is a temperature scale that is named after the Swedish astronomer Anders Celsius , who developed a similar temperature scale two years before his death....
), and at a barometric pressure of 30 inches of mercury
Inch of mercury

Inches of mercury, inHg or "Hg is a measuring unit for pressure. It is still widely used for barometric pressure in weather reports and aviation in the United States, but is considered somewhat outdated elsewhere....
, was determined to weigh 252.458 troy grain
Grain (measure)

In many cultures, a grain is a Physical unit of measurement of mass that is based upon the mass of a single seed of a typical cereal. Historically, in Europe, the average masses of wheat and barley grain were used to define units of mass....
s (gr).

Troy ounce

The troy ounce (ozt) is 480 grains, somewhat heavier than an avoirdupois
Avoirdupois

The avoirdupois system is a system of Units of measurement based on a pound of sixteen ounces. It is the everyday system of weight used in the United States....
 ounce (437.5 grains). A grain is exactly 64.79891 mg; hence one troy ounce is exactly 31.1034768 g
Gram

The gram , ; symbol g, is a Physical 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" , a gram is now defined as one one-thousandth of the SI base unit, the kilogram, or Scientific notation kg, which itself is...
, about 10 percent more than the avoirdupois ounce, which is exactly 28.349523125 g. The troy ounce is traditionally used over the avoirdupois ounce in the pricing of precious metals, gold
Gold

Gold is a chemical element with the symbol Au and atomic number 79. It is a highly sought-after precious metal, having been used as money, as a store of value, in jewelry, in sculpture, and for ornamentation since the beginning of recorded history....
, platinum
Platinum

Platinum is a chemical element with the chemical symbol Pt and an atomic number of 78. Its name is derived from the Spanish term platina del Pinto, which is literally translated into "little silver of the Pinto River." It is in Group 10 of the periodic table of elements....
, and silver
Silver

Silver is a chemical element with the chemical symbol Ag and atomic number 47. A soft, white, lustrous transition metal, it has the highest electrical conductivity of any element and the highest thermal conductivity of any metal....
. The grain, which is identical in both the troy and avoirdupois systems, is used to measure arrow and arrowhead weights in archery
Archery

Archery is the art, practice or skill of shooting with Bow and arrow. Archery has historically been used in hunting and combat and has become a precision sport....
 and bullets and powder weights in ballistics
Ballistics

Ballistics is the science of mechanics that deals with the flight, behavior, and effects of projectiles, especially bullets, gravity bombs, rockets, or the like; the science or art of designing and accelerating projectiles so as to achieve a desired performance....
. The grain is also common to the apothecaries system and was long used in medicine, but has been largely replaced by milligrams.

Pennyweight dwt

There are 24 grains in 1 dwt, and 20 dwt in one Troy Ounce.

Troy pound

The troy pound (troy) is 5,760 gr (˜ 373.24 g, 12 ozt), while an avoirdupois pound is heavier at 7,000 gr (˜ 453.59 g).

There are 12 troy ounces per troy pound, rather than 16 avoirdupois ounces (oz)
Ounce

This article is about the unit of mass. For the unit of force, see Pound-force. For the unit of volume, see Fluid ounce. For all other uses, see Ounce ....
 in the avoirdupois pound (lb) as in the more common avoirdupois system. The avoirdupois pound is 147/12 (˜ 14.583) troy ounces.

Scottish system

In Scotland the Incorporation of Goldsmiths of the City of Edinburgh used a system in multiples of sixteen. (See Assay-Master's Accounts, 1681-1702, on loan from the Incorporation to the National Archives of Scotland.) Thus there were 16 drops to the troy ounce, 16 ounces to the troy pound, and 16 pounds to the troy stone. The Scots had several other ways of measuring precious metals and gems, but this was the common usage for silver and gold.

Conversions

Unit Grains Grams
Troy pound (12 troy ounces) 5,760 373.241 721 6
Troy ounce (20 pennyweights) 480 31.103 476 8
Pennyweight 24 1.555 173 84
Grain 1 0.064 798 91


The troy system was used in the Apothecaries' system
Apothecaries' system

The apothecaries' system of weights is a historical system of mass units that were used by physicians and apothecary for medical recipes, and also sometimes by scientists....
, but with different further subdivisions.

Relationship to British coinage

The troy system was the basis for the pre-decimalisation British system of coinage
British coinage

The standard circulating coinage of the United Kingdom is denominated in pound sterling , and, since the introduction of the two pound coin in 1998, ranges in value from one penny to two pounds....
 introduced by Henry II of England
Henry II of England

Henry II, called Curtmantle ruled as King of England , Count of Anjou, Duke of Normandy, Duke of Aquitaine, Duke of Gascony, Count of Nantes, Lord of Ireland and, at various times, controlled parts of Wales, Scotland and western France....
, in which the penny
Penny

A penny is a coin or a unit of currency used in several English-speaking countries....
 was literally one pennyweight
Pennyweight

A pennyweight is a unit of mass which is the same as 24 Grain , 1/240th of a troy pound, 1/20th of a troy ounce, approximately 0.055 ounces or approximately 1.555 grams....
 of silver. One pound sterling
Pound sterling

----The pound sterling , subdivided into 100 pence , is the currency of the United Kingdom, its Crown dependency and the British Overseas Territories of South Georgia and the South Sandwich Islands and British Antarctic Territory....
 was equal to twenty shilling
Shilling

The shilling is a unit of currency used in current and former Commonwealth of Nations countries, and continued to be used in countries that left the commonwealth, such as Republic of Ireland and Tanzania....
s, with each shilling equal to twelve pennies
Penny

A penny is a coin or a unit of currency used in several English-speaking countries....
. Thus, one pound sterling equals 240 pennyweights, or one troy pound of sterling silver.

See also

  • Carat (mass)
    Carat (mass)

    The carat is a unit of mass used for measuring gemstones and pearls . Currently a carat is defined as exactly 200 milligram . This definition, known as the metric carat, was adopted in 1907 at the Fourth General Conference on Weights and Measures, and soon afterwards in many countries around the world....
  • Conversion of units
    Conversion of units

    Conversion of units refers to conversion factors between different units of measurement for the same quantity....
  • Mark (weight)
    Mark (weight)

    The mark was originally a unit of mass for gold and silver common throughout western Europe, and was equal to 8 troy ounces . Variations throughout the Middle Ages were, however, considerable....
  • - essay on the history of the Troy Ounce with many links to further reading.