Understanding Stone and Kilograms
The stone (abbreviated st) is a unit of weight equal to 14 pounds or 6.35029 kilograms. It belongs to the Imperial system of measurements and has been in use across the British Isles for centuries. Unlike many other Imperial units that have fallen out of daily use, the stone remains firmly embedded in British and Irish culture, particularly when it comes to describing body weight.
The kilogram (abbreviated kg) is the base unit of mass in the International System of Units (SI). It is the standard unit of weight used by the vast majority of the world's population, including all of continental Europe, Asia, Africa, South America, and Oceania. One kilogram equals approximately 2.20462 pounds or 0.15747 stone.
Historically, the stone was not a fixed quantity. In medieval England, the stone varied depending on the commodity being weighed: a stone of wool weighed 14 pounds, but a stone of glass weighed 5 pounds, and a stone of sugar weighed 8 pounds. It was not until 1835 that the British Weights and Measures Act standardised the stone at exactly 14 avoirdupois pounds (6.35029 kg) for all purposes.
How to Convert Stone to Kilograms
The conversion formula is straightforward: multiply the number of stone by 6.35029 to get the equivalent weight in kilograms. For example, 10 stone × 6.35029 = 63.503 kg. This factor comes directly from the definition: 1 stone = 14 pounds, and 1 pound = 0.45359237 kg, so 14 × 0.45359237 = 6.35029318 kg.
When converting a combined stone-and-pounds value (which is how most people express their weight in the UK), you have two options:
- Method 1: Convert stone to pounds (multiply by 14), add the extra pounds, then multiply the total by 0.453592 to get kg. Example: 11st 7lb = (11 × 14) + 7 = 161 lbs = 161 × 0.453592 = 73.03 kg.
- Method 2: Convert stone to kg directly (multiply by 6.35029), convert the extra pounds separately (multiply by 0.453592), and add the two results. Example: 11st 7lb = (11 × 6.35029) + (7 × 0.453592) = 69.853 + 3.175 = 73.028 kg.
Both methods give the same answer. Use whichever feels more intuitive. The converter at the top of this page handles the calculation automatically for any value you enter.
International Travel: UK vs Metric Countries
If you are travelling from the United Kingdom or Ireland to a country that uses the metric system (which includes most of the world), you will need to know your weight in kilograms. Airline baggage allowances, hotel gym equipment, medical consultations abroad, and pharmacy scales all display weight in kilograms.
Before your trip, converting your body weight from stone to kilograms is a useful preparation step. A few common reference points can help: 10 stone is about 63.5 kg, 12 stone is about 76.2 kg, and 14 stone is about 88.9 kg. Knowing your approximate weight in kilograms also helps when purchasing clothing in metric-sized countries, as size charts often reference weight ranges in kg.
Conversely, if you are visiting the UK from a metric country, understanding stone values will help you follow conversations about weight loss, fitness goals, and health targets that are universally expressed in stone by British and Irish people.
Medical Records and Health Services
The National Health Service (NHS) in the UK uses both stone and kilograms, depending on the context. Official medical records and clinical systems typically store weight in kilograms, as this is the international standard for medical practice. However, patient-facing materials, weight management programmes, and GP consultations often present weight in stone and pounds because that is what patients understand.
The NHS BMI calculator accepts input in either stone/pounds or kilograms. When calculating BMI from stone, the formula is: convert stone to kg (stone × 6.35029), then divide by height in metres squared. For example, a person who is 12 stone (76.2 kg) and 1.75 m tall has a BMI of 76.2 / (1.75 × 1.75) = 24.9, which sits right at the upper boundary of the "healthy weight" range.
If you need to provide your weight in kilograms for a medical form, immigration application, or insurance document, converting from stone is essential. Many official forms worldwide require weight in kg, so knowing the conversion factor of 6.35029 is practical knowledge for anyone who thinks in stone.
Immigration and Visa Forms
Some immigration and visa applications, particularly for countries like Australia, New Zealand, and Canada, require applicants to provide their weight in kilograms as part of the medical examination. If you normally think of your weight in stone, you will need to convert before filling out these forms.
The conversion is simple and exact: multiply your stone value by 6.35029. If your weight includes extra pounds (e.g., 13 stone 5 pounds), convert the total to pounds first (13 × 14 + 5 = 187 lbs) and then multiply by 0.453592 to get 84.82 kg. Alternatively, use the converter at the top of this page for an instant result.
Exercise and Gym Use
Many gym machines, fitness apps, and workout programmes worldwide use kilograms as their standard unit. If you join a gym abroad or use an internationally developed fitness app, you may need to enter your body weight in kilograms. Weightlifting plates in most countries outside the US are measured in kilograms, and understanding the stone-to-kg conversion helps you set appropriate weights for exercises.
Popular fitness trackers and apps such as MyFitnessPal, Strava, and Apple Health all support both stone and kilograms. However, when sharing data with trainers, nutritionists, or online fitness communities that operate in metric, converting your weight to kilograms ensures clear communication and accurate calorie and macro calculations.
Conversion Table
| Stone (st) | Kilograms (kg) |
|---|---|
| 1 st | 6.350 kg |
| 2 st | 12.701 kg |
| 3 st | 19.051 kg |
| 4 st | 25.401 kg |
| 5 st | 31.751 kg |
| 6 st | 38.102 kg |
| 7 st | 44.452 kg |
| 8 st | 50.802 kg |
| 9 st | 57.153 kg |
| 10 st | 63.503 kg |
| 11 st | 69.853 kg |
| 12 st | 76.203 kg |
| 13 st | 82.554 kg |
| 14 st | 88.904 kg |
| 15 st | 95.254 kg |
| 16 st | 101.605 kg |
| 17 st | 107.955 kg |
| 18 st | 114.305 kg |
| 19 st | 120.656 kg |
| 20 st | 127.006 kg |
Recent Cases
Facts
- One stone equals exactly 14 pounds or 6.35029 kilograms.
- The stone was standardised at 14 pounds by the British Weights and Measures Act of 1835.
- In the UK and Ireland, body weight is still most commonly expressed in stone and pounds.
- The word "stone" as a unit of weight dates back to at least the 14th century in English trade records.
- Australia used stone until the 1970s metric switchover; the UK never fully abandoned it for body weight.
Frequently Asked Questions
One stone equals exactly 6.35029 kilograms (or 14 pounds). This conversion factor is the internationally recognised definition of the stone unit. To convert stone to kg, multiply the number of stone by 6.35029.
Multiply the number of stone by 6.35029 to get kilograms. For example, 12 stone × 6.35029 = 76.203 kg. If you have stone and pounds (e.g., 12st 7lb), first convert everything to pounds (12 × 14 + 7 = 175 lbs), then multiply by 0.453592 to get 79.38 kg.
10 stone is equal to 63.503 kilograms (10 × 6.35029 = 63.5029). This is a common body weight, roughly equivalent to 140 pounds. It falls within the healthy BMI range for many average-height adults.
The stone has been used in the British Isles for centuries as a unit of weight. The United Kingdom and Ireland continue to use stone for body weight in everyday conversation, even though both countries have officially adopted the metric system. It persists due to deep cultural habit and the fact that stone values for body weight are small, memorable numbers.
The stone was officially removed from the list of legally recognised trade units in the UK in 1985 as part of metrication. However, it was never banned for informal use, and it remains the most common way to express body weight in the UK and Ireland. The NHS, fitness programmes, and everyday conversation all continue to use stone.