How to Convert Kilograms to Stones
Converting kilograms to stone is a common requirement for people in the United Kingdom and Ireland, where body weight is traditionally expressed in stone and pounds. The kilogram (kg) is the SI base unit of mass used worldwide, while the stone (st) is an imperial unit equal to 14 pounds, primarily used in the British Isles for expressing human body weight. One kilogram equals approximately 0.157473 stone. This conversion is particularly relevant for British travelers or expatriates who need to translate medical weight readings from kilograms, for fitness and weight-loss applications serving UK audiences, and for healthcare professionals working in environments where both measurement systems are in use. Although the stone is not an officially recognized SI unit and has been largely replaced by kilograms in most commercial and scientific contexts, it remains deeply embedded in British and Irish culture for personal weight measurement. Understanding this conversion allows for seamless communication between metric-based health systems and the cultural preference for stone in everyday conversation.
Conversion Formula
To convert kilograms to stone, multiply the mass in kilograms by 0.157473. This conversion factor is derived from the fact that one stone equals exactly 14 avoirdupois pounds, and one pound equals 0.45359237 kilograms. Therefore, one stone equals 6.35029318 kilograms, and dividing 1 by 6.35029318 gives approximately 0.157473 stone per kilogram.
Stone = Kilograms × 0.157473
5 kilograms = 0.78737 stones
Step-by-Step Example
To convert 5 kilograms to stone:
1. Start with the value: 5 kilograms
2. Multiply by the conversion factor: 5 × 0.157473
3. Calculate: 5 × 0.157473 = 0.78737
4. Result: 5 kilograms = 0.78737 stone
Since stone is typically used for body weight, a more practical example would be 70 kg = 11.023 stone, which is approximately 11 stone and 0.3 pounds.
Understanding Kilograms and Stones
What is a Kilogram?
The kilogram was established in 1795 during the French Revolution as part of the metric system, originally defined as the mass of one liter of water at its densest temperature. The physical International Prototype of the Kilogram (IPK), a platinum-iridium cylinder created in 1889, served as the global standard for over a century. In a historic change, the kilogram was redefined in 2019 based on the Planck constant, severing its dependence on any physical artifact. Today, the kilogram is the most widely used unit of mass globally, anchoring measurements in science, industry, and daily life across virtually every nation.
What is a Stone?
The stone as a unit of weight has ancient origins, with archaeological evidence suggesting that stones of standard weight were used for trade in antiquity. In medieval England, the stone was standardized at different values depending on the commodity being weighed: a stone of wool differed from a stone of meat. By the 14th century, King Edward III standardized the wool stone at 14 pounds, and this value eventually became the universal definition. The Weights and Measures Act of 1835 officially defined the stone as 14 avoirdupois pounds. Although the stone was formally removed from legal use in trade under EU metrication directives, it remains culturally embedded in British and Irish daily life for measuring body weight.
Practical Applications
Kilogram-to-stone conversion is essential in UK healthcare, where hospital scales often display weight in kilograms but patients expect to hear their weight in stone. British weight-loss programs and fitness apps frequently need to display weights in both units to serve their audience. International weight-class sports like boxing and horse racing use stone in the UK while other countries use kilograms, necessitating conversion. Clothing size charts from European manufacturers may list weight ranges in kilograms that UK consumers need to convert to stone for reference. Immigration and visa medical examinations in the UK may require weight conversion between the two systems.
Tips and Common Mistakes
A common mistake is forgetting that one stone equals 14 pounds, not 10 or 16. When converting to stone, the result often includes a fractional stone value that people prefer to express as stone and pounds. To do this, take the whole number as stone, then multiply the decimal remainder by 14 to get pounds. For example, 10.5 stone is 10 stone 7 pounds (0.5 × 14 = 7). Another error is using the stone unit outside the UK and Ireland, where it is not widely understood. Be careful to distinguish between the stone (14 pounds) and the metric tonne or US ton, which are entirely different units despite potentially similar-sounding names.
Frequently Asked Questions
70 kilograms is approximately 11.023 stone, or about 11 stone 0.3 pounds. To express this in the traditional British format, 70 kg is roughly 11 stone 0 pounds, since 0.023 stone times 14 is only about 0.32 pounds. This is a common reference point since 70 kg is near the average adult body weight.