Stone to Kilograms Converter

How to Convert Stone to Kilograms

Converting stone to kilograms is a straightforward calculation used daily by millions of people in the United Kingdom and Ireland. One stone equals exactly 6.35029 kilograms, which is also exactly 14 pounds. To convert any weight in stone to kilograms, simply multiply by 6.35029.

For example, if you weigh 11 stone, your weight in kilograms is 11 × 6.35029 = 69.85 kg. If your weight includes extra pounds (such as "11 stone 7 lb"), first convert the total to decimal stone: 11 + (7 ÷ 14) = 11.5 stone, then multiply: 11.5 × 6.35029 = 73.03 kg.

The stone is one of the few traditional British units still in common everyday use. While the UK officially adopted the metric system for most purposes, body weight remains stubbornly imperial in casual conversation. You will hear people say "I weigh ten stone" rather than "I weigh 63.5 kilograms," even though medical records, gym equipment, and official documents increasingly use kilograms.

This converter handles both directions: enter stone to get kilograms, or enter kilograms to get stone. It uses the exact conversion factor of 6.35029 kg per stone, giving you precise results suitable for medical records, fitness tracking, and any other application where accuracy matters.

Stone to Kilograms Conversion Chart

This comprehensive reference table covers the most common body weight ranges expressed in stone and their kilogram equivalents. The table includes both whole stone values and common stone-and-pound combinations for easy lookup.

For values not listed in the table, use our converter above or apply the formula: kilograms = stone × 6.35029. For stone-and-pounds values, convert pounds to decimal stone first by dividing the pounds by 14.

History and Origin of the Stone Unit

The stone is one of the oldest units of weight in the British system, with origins dating back to at least the 14th century. The name comes from the practice of using actual stones as counterweights on balance scales — a method of weighing goods that predates standardized metal weights.

Historically, the stone varied significantly by commodity and region. A stone of wool weighed 14 pounds, a stone of butcher's meat weighed 8 pounds, and a stone of cheese weighed 16 pounds in some areas. This inconsistency caused considerable confusion in trade and commerce.

In 1389, a royal statute under King Edward III established the stone of wool at 14 pounds (6.35 kg), and this became the most widely used definition. The Weights and Measures Act of 1835 officially standardized the stone at 14 avoirdupois pounds across the United Kingdom, eliminating the regional variations that had persisted for centuries.

When the UK began adopting the metric system in the 1960s and 1970s, the stone was officially dropped from trade and commerce. The Weights and Measures Act 1985 removed it as a legally recognized unit for trade purposes. However, no legislation has prevented its use in everyday life, and it has persisted as the default way British and Irish people discuss body weight.

Interestingly, the stone was historically used in North America as well. It appeared in early American commerce and was used for weighing livestock and produce. However, it fell out of favor in the United States during the 19th century as Americans standardized on pounds alone. Today, the stone is essentially exclusive to the UK and Ireland, with most other English-speaking countries using either kilograms or pounds.

Where the Stone Is Still Used Today

Despite being officially obsolete for trade purposes, the stone remains deeply embedded in daily life in the United Kingdom and Ireland. Here are the main contexts where you will encounter it:

Personal body weight. This is by far the most common use. When British people discuss their weight casually, they almost always use stone and pounds. "I need to lose a stone" or "She weighs about nine stone" are everyday expressions. Bathroom scales sold in the UK typically display weight in stone, pounds, and kilograms.

Healthcare settings. While NHS medical records have officially transitioned to kilograms, many British patients still report their weight to doctors and nurses in stone. Healthcare professionals are trained to convert between the two, and most clinical scales display both units.

Fitness and sports. Boxing weight classes in the UK are traditionally described in stone (bantamweight is about 8 stone 6 lb, middleweight is about 11 stone 6 lb). Horse racing uses stone for jockey weights. Gyms in the UK often have plates and displays marked in both stone/pounds and kilograms.

Media and journalism. British newspapers and magazines commonly report celebrity weights, diet results, and health statistics in stone. Weight-loss stories ("Woman loses 4 stone in 6 months") are a staple of UK tabloid journalism.

Ireland. The Republic of Ireland uses stone as commonly as the UK for body weight, despite having been fully metric for decades. This is one of the few areas where pre-metric measurements persist in Irish daily life.

Outside the UK and Ireland, the stone is virtually unknown. Americans use pounds, while the rest of the world uses kilograms. This can cause confusion for British travelers or expatriates who need to express their weight in a unit that others understand.

Stone to kg Conversion for BMI and Health

Body Mass Index (BMI) calculations require weight in kilograms and height in meters. Since many people in the UK know their weight in stone but need kilograms for health assessments, converting between the two is a regular necessity.

The BMI formula is: BMI = weight (kg) ÷ height (m)². For example, a person who weighs 12 stone (76.2 kg) and is 1.75 m tall has a BMI of 76.2 ÷ (1.75 × 1.75) = 76.2 ÷ 3.0625 = 24.9, which is at the upper end of the "healthy weight" range.

Here is a reference showing BMI categories with weight ranges in both stone and kilograms for a person of average height (1.70 m / 5 ft 7 in):

Remember that BMI is a screening tool, not a diagnostic measure. It does not account for muscle mass, bone density, age, or body composition. Athletes and very muscular individuals often have a high BMI despite being in excellent health. Consult a healthcare professional for a comprehensive health assessment.

Converting Stone and Pounds to Kilograms Step by Step

Many people express their weight in stone and pounds (for example, "10 stone 7 pounds" or "10 st 7 lb"). Converting this combined format to kilograms requires an extra step compared to whole stone values. Here is the process:

Step 1: Convert the whole stone portion to kilograms by multiplying by 6.35029.
Example: 10 stone × 6.35029 = 63.50 kg

Step 2: Convert the remaining pounds to kilograms by multiplying by 0.453592.
Example: 7 pounds × 0.453592 = 3.18 kg

Step 3: Add the two results together.
Example: 63.50 + 3.18 = 66.68 kg

So 10 stone 7 pounds = 66.68 kg.

An alternative method is to first convert everything to pounds: (10 × 14) + 7 = 147 pounds. Then convert pounds to kilograms: 147 × 0.453592 = 66.68 kg. Both methods give the same result.

For the reverse conversion (kg to stone and pounds): divide the kilogram value by 6.35029 to get decimal stone. The whole number is the stone portion. Multiply the decimal remainder by 14 to get the pounds. For example, 75 kg ÷ 6.35029 = 11.81 stone. The whole portion is 11 stone. The remainder is 0.81 × 14 = 11.3 pounds, so 75 kg ≈ 11 stone 11 lb.

Stone vs Other Weight Units Comparison

Understanding how the stone relates to other common weight units helps when communicating weight across different countries and systems:

The key relationship to remember is that 1 stone = 14 pounds = 6.35 kg. Since 14 is a convenient number to work with (divisible by 2 and 7), stone-and-pounds arithmetic is relatively straightforward compared to conversions involving irregular numbers.