For many people outside the United Kingdom and Ireland, the term “stone” appears frequently as a unit of measurement for body weight. This historical unit remains the standard way to express personal weight in these regions, often confusing those accustomed to the metric system or the US customary system of pounds. Understanding what a stone represents is the first step toward interpreting global weight loss information and tracking progress. This article clarifies the stone unit, its historical context, and its practical application in a weight loss journey.
Defining the Stone Weight Unit
The stone is a unit of mass within the British imperial system, defined precisely in terms of the more familiar pound. One stone is equal to 14 avoirdupois pounds (lbs) exactly. The stone is commonly abbreviated as “st” and is used almost exclusively for measuring human body weight in countries like the United Kingdom and Ireland. For those who use the metric system, one stone converts to approximately 6.35 kilograms (kg).
Weight is often expressed as a combination of stones and pounds, such as “12 stone 4 pounds.” This format represents a total weight of 172 pounds (12 multiplied by 14, plus the additional 4 pounds). Understanding these conversions is necessary when interpreting weight charts or medical records from these countries.
The Origins of the Stone Measurement
The history of the stone measurement stretches back into antiquity, originating from the practical use of physical stones as standard weights for commerce and trade. The unit’s value was not initially uniform, varying widely across different regions and depending on the commodity being weighed.
A key standardization occurred in the mid-14th century when a statute during the reign of King Edward III fixed the stone of wool and other merchandise at 14 pounds. This 14-pound definition became the accepted legal standard that was eventually adopted into the Imperial system. Although the stone was officially removed from the list of units permitted for trade in the United Kingdom by the Weights and Measures Act 1985, its customary use for personal body weight has persisted.
Using Stones to Track Weight Loss
When tracking weight loss, the stone unit is used in a fractional system combining stones and pounds. A person’s weight is recorded as the number of full stones plus the remaining pounds, such as “13 st 6 lbs.” To determine the total weight in pounds, one multiplies the number of stones by 14 and adds the remaining pounds (13 x 14 + 6 = 188 lbs).
Converting a current weight into this format requires dividing the total pounds by 14. The whole number result is the stones, and the remainder is the pounds. For example, if a person weighs 165 pounds, dividing 165 by 14 yields 11 with a remainder of 11, meaning their weight is 11 stone 11 pounds.
The use of the stone unit for tracking weight loss offers a distinct psychological advantage for some individuals. Because one stone represents a loss of 14 pounds, it functions as a larger, less frequent milestone compared to tracking in single pounds or kilograms. This larger interval can help shift the focus away from minor daily weight fluctuations, emphasizing long-term progress.
A weight loss goal of “losing a stone” is a common and tangible objective, equivalent to shedding 6.35 kilograms. For those with substantial weight to lose, achieving a milestone like dropping from 16 stone to 15 stone can be a powerful motivator. This format frames the journey in terms of major accomplishments.
To convert weight loss milestones, a loss of 1 stone is 14 pounds, 2 stone is 28 pounds, and 3 stone is 42 pounds. In metric terms, these milestones are 6.35 kg, 12.7 kg, and 19.05 kg. Understanding these equivalencies is helpful for setting realistic goals and communicating progress with people who use different systems of measurement.