Converting weights

Updated on by Stefan Banse

Units of weight have developed historically and have differed from country to country. Even in the various branches of science or, for example, the trades, different units of measurement were always common. In the meanwhile, the metric system, with the kilogram as the base unit for weight in the SI International System of Units (Système international d'unités), was established for purposes of standardization. Nevertheless, other units that are not part of the metric system continue to be commonly used . Especially in the Anglo-American system, the weight units of ton, hundredweight, pound, ounce, dram and grain are used for historical reasons. All of these units of weight can easily be converted into each other with the following weight calculator

Tips on use

Enter the weight to be converted and choose from and to which unit of weight this value is to be converted. The weight converter provides the most common metric and Anglo-American weight measures for the calculation. For more information on the various units of weight, use the help buttons with question marks on the calculator.

Popular converters from practice

  • Conversion from kilogram (kg) to pound (lb)
  • Conversion from ton to kilogram (kg)
  • Conversion from pound (lb) to gram (g)

Metric units of weight

The metric system is the system of units with the kilogram as the base unit for the weight or mass. Unlike other systems of units, decimal multiples or decimal fractions can easily be calculated here. Among other, it includes the following units of weight:

Ton (t)

The unit ton belongs to the metric system and is derived from the basic unit kilogram. 1 metric ton can be converted into 1,000 kilograms, and 1 kilogram is equivalent to 0.001 metric tons. The ton belongs to the International System of Units (SI).

Kilogram (kg)

The kilogram is the basic unit of mass, i.e., the weight in the International System of Units (SI) and in other metric systems. It has been determined since 1889 by the mass of the international kilogram prototype, or the original kilogram. This is a platinum-iridium cylinder kept in a safe by the International Bureau of Weights and Measures in Paris. All other units of mass or weight in the metric system are derived from the kilogram (e.g., 1 t = 1,000 kg, 1 kg = 1,000 g).

Hectogram (hg)

The unit hectogram belongs to the metric system and is derived from the basic unit kilogram. 1 kilogram is equivalent to 10 hectograms, and 1 hectogram is equivalent to 0.1 kilograms. According to the conversion into kilograms, the hectogram is defined in national systems of units and standards.

Gram (g)

The unit gram also belongs to the metric system and is derived from the basic unit kilogram. 1 kilogram is equivalent to 1,000 grams, and 1 gram is equivalent to 0.001 kilograms. According to the conversion to kilogram, the gram is defined in national systems of units and standards.

Centigram (cg)

The unit centigram also belongs to the metric system and is derived from the basic unit kilogram. 1 kilogram is equivalent to 100,000 centigrams, and 1 centigram is equivalent to 0.00001 kilograms. The centigram is also defined in national systems of units and standards in accordance with the conversion into kilograms.

Milligram (mg)

The unit milligram belongs to the metric system and is derived from the basic unit kilogram. 1 kilogram is equivalent to one million milligrams, and 1 milligram is equivalent to one millionth of a kilogram. According to the conversion into kilograms, the milligram is defined in national systems of units and standards.

Microgram (μg)

The unit microgram also belongs to the metric system and is derived from the basic unit kilogram. One kilogram is equivalent to one billion micrograms, and one microgram is equivalent to one billionth of a kilogram. According to the conversion into kilograms, the microgram is defined in national systems of units and standards.

Nanogram (ng)

Finally, the unit nanogram also belongs to the metric system and is derived from the base unit kilogram. One kilogram is equivalent to one trillion nanograms, and one nanogram is equivalent to one trillionth of a kilogram. According to the conversion into kilograms, the nanogram is defined in national systems of units and standards.

Carat (kt)

The carat unit is primarily used for weighing gemstones. The carat belongs to the metric system and is derived from the basic unit kilogram. 1 carat is equivalent to 0.2 grams, and 1 carat is equivalent to 0.0002 kilograms. According to the conversion into kilograms, the carat is defined in national systems of units and standards. It is a legal unit in the countries of the EU but does not belong to the International System of Units (SI).

Atomic mass unit (u)

The atomic mass unit is used to specify atomic and molecular masses. The value is fixed at 1/12 of the mass of an atom of the carbon isotope 12C. Thus, 1 u corresponds approximately to the mass of a proton or neutron. The unit symbol "u" stands for unified atomic mass unit. The atomic mass unit belongs to the International System of Units and is derived from the base unit kilogram. 1 u is equivalent to 1.660538921x10-27 kilograms.

Other metric units of weight

There are numerous other SI units of weight, which ultimately represent a multiple or fraction of the gram. For this purpose, so-called unit prefixes, i.e., prefixes for the gram, are formed as in the previous examples. The following table provides an overview:

Symbol Name Value
Short scaleLong scaleUnit
Yg Yottagram 1024 septillion quadrillion grams
Zg Zettagram 1021 sextillion trilliard grams
Eg Exagram 1018 quintillion trillion grams
Pg Petagram 1015 quadrillion billiard grams
Tg Teragram 1012 trillion billion grams
Gg Gigagram 109 billion milliard grams
Mg Megagram 106 million grams
kg Kilogram 103 thousand grams
hg Hectogram 102 hundred grams
dag Decagram 101 ten grams
g Gram 100 one gram
dg Decigram 10-1 tenth of a gram
cg Centigram 10-2 hundredth of a gram
mg Milligram 10-3 thousandth of a gram
µg Microgram 10-6 millionth of a gram
ng Nanogram 10-9 billionth milliardth of a gram
pg Picogram 10-12 trillionth billionth of a gram
fg Femtogram 10-15 quadrillionth billiardth of a gram
ag Attogram 10-18 quintillionth trillionth of a gram
zg Zeptogram 10-21 sextillionth trilliardth of a gram
yg Yoctogram 10-24 septillionth quadrillionth of a gram

Anglo-American units of weight

The Anglo-American units of weight have their origins in medieval England. Many of them were sizes that can be measured by everyday objects, such as grain, stone or dram. Over time, they were largely unified and finally the metric system was used as the yardstick for most Anglo-American weight units. They do not, however, belong to the International System of Units, i.e., they are not SI-compliant.

Long ton (tn.l.)

In outdated terms, the long ton is also called the "British ton". It is equivalent to 20 "long hundredweight" or 2,240 pounds. As with the short ton, a long ton is equivalent to 20 hundredweight. The unit hundredweight differs in the British and American systems, however. While in America a hundredweight is defined as 100 pounds, in the Anglo-Saxon world it is defined as 112 pounds. Thus: one long ton is equivalent to 20 long hundredweight, which in turn is equivalent to 2,240 pounds and thus 1,016.0469088 kilograms. The long ton is used in particular for the standard displacement of a ship fixed in Washington in 1922. By the way, the well-known unit of "ton" from the metric system, which is defined as 1,000 kilograms, is consequently called the metric ton in the Anglo-American area to differentiate from the long ton and short ton.

Short ton (tn.sh.)

In outdated terms, the short ton is also known as "American ton" and is especially common in the USA. It is equivalent to 20 "short hundredweight" or 2,000 pounds. As with the long ton, a short ton is equivalent to 20 hundredweight. The unit hundredweight differs in the British and American systems, however. While in America a hundredweight is defined as 100 pounds, in the Anglo-Saxon world it is defined as 112 pounds. Thus: one short ton is equivalent to 20 short hundredweight, which in turn is equivalent to 2,000 pounds and thus 907.18474 kilograms. By the way, the well-known unit "ton" from the metric system, which is defined as 1,000 kilograms, is consequently called the metric ton in the Anglo-American area to differentiate from the long ton and short ton.

Long hundredweight (cwt.l.)

In outdated terms, the long hundredweight is also known as the "British hundredweight", where it is common and is equivalent to 112 pounds or 50.80234544 kilograms. The term "hundredweight" is roughly equivalent to the German term "Zentner".

Short hundredweight (cwt.sh.)

The short hundredweight is also known as the "American hundredweight", where it is common and is equivalent to 100 pounds or 45.359237 kilograms. The term "hundredweight" is roughly equivalent to the German term "Zentner".

Stone (st)

The stone unit of weight is a British non-SI unit which was an official unit in Great Britain until 1985. One stone is equivalent to 14 pounds or 6.35029318 kilograms. As an unofficial unit in Great Britain for human body weight, a stone has a similar significance as the obsolete and abolished units of kilocalorie or PS in Germany.

Pound (lb)

The pound does not belong to the SI International System of Units (Système international d'unités) either. Many different definitions were used, but today the international avoirdupois pound is the most common unit and is officially defined as exactly 0.45359237 kilograms. Thus, 1 pound is equivalent to 0.45359237 kilograms, and one kilogram is equivalent to 2.20462262 pounds. The avoirdupois pound described here is equivalent to 16 ounces and should not be confused with the troy pound, which is now used only rarely for precious metals and is derived from the troy ounce.

Ounce (oz.)

The common ounce (English: international avoirdupois ounce) as unit of weight is very common in the Anglo-American area but does not belong to the International System of Units. It should not be confused with the troy ounce or apothecaries' ounce and is frequently used in many countries to indicate the weight of foods. 1 ounce is equivalent to 28.349523125 grams, and one gram is equivalent to 0.035273961 ounces.

Troy ounce (oz.tr.)

The troy ounce as a unit of weight does not belong to the International System of Units but is used for precious metals. Its weight corresponds to that of the apothecaries' ounce but refers only to the precious metal content. 1 troy ounce is equivalent to 31.1034768 grams, and 1 gram is equivalent to 0.0321507466 troy ounces.

Apothecaries' ounce (oz.ap.)

The apothecaries' ounce as a unit of weight does not belong to the International System of Units but is used for medicines and chemicals. Its weight is equivalent to that of the a troy ounce. 1 apothecaries' ounce is equivalent to 31.1034768 grams, and 1 gram is equivalent to 0.0321507466 apothecaries' ounces'.

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Source information

As source for the information in the "Units of weight" category, we have used in particular:

Last update on June 25, 2020

The last changes in the "Units of weight" category were implemented by Stefan Banse on June 25, 2020. The main changes were:

  • Publication of the Weight converter
  • Creation of the texts for the corresponding pages
  • Editorial revision of all texts in this category