Stone (st)
The stone is an imperial unit of mass equal to 14 pounds or approximately 6.35 kilograms. It is used almost exclusively in the United Kingdom and Ireland for expressing human body weight. While Americans weigh themselves in pounds and most of the world uses kilograms, the British commonly say "I weigh eleven stone four" rather than giving a figure in pounds or kilograms.
Definition
One stone equals exactly 14 avoirdupois pounds, 224 ounces, or approximately 6.35029 kilograms. It is not recognised as a legal unit of measurement for trade in the UK or EU, and it has no equivalent in the US customary system, where pounds alone are used. Body weight in stone is typically expressed as "X stone Y pounds" for the remainder, such as "10 stone 7" meaning 147 pounds.
History
The stone has been used as a unit of weight in the British Isles since at least the 14th century, though its value varied widely by region and commodity. A stone of wool differed from a stone of cheese, which differed from a stone of glass. Values ranged from 4 to 26 pounds depending on the product and locality. In 1824, the British Weights and Measures Act standardised the stone at exactly 14 avoirdupois pounds. When the United Kingdom adopted the metric system for trade in 1985, the stone lost its legal status for commercial use, but it endures as the default unit for personal weight in British and Irish culture.
Common Uses
In the United Kingdom and Ireland, personal body weight is overwhelmingly given in stone and pounds. Bathroom scales sold in the UK often display stone alongside kilograms. Medical records in the NHS have historically used stone, though metric units are becoming standard. Boxing weight classes in British boxing organisations sometimes reference stone. Outside of body weight, the unit has very few modern applications. The stone is virtually unknown in the United States, continental Europe, and most other countries.
Did You Know? Facts About Stone
- A stone of wool in medieval England was 14 pounds, but a stone of sugar was 8 pounds and a stone of glass was 5 pounds - the value depended entirely on the commodity.
- The average British adult male weighs about 13 stone 3 (185 pounds / 84 kg), according to NHS data.
- The phrase "stone cold" originally referred to the weight and chill of actual stone, not to the temperature scale.
- Irish passports list weight in kilograms, but most Irish people will tell you their weight in stone if asked.
- The stone is the only imperial unit that is commonly used in the UK but completely absent from US customary usage.