Stone to KG Converter

If you've ever tried to convert your weight from stone to kilograms, you're not alone. The United Kingdom has a unique relationship with weight measurements, using both imperial stone and metric kilograms depending on the context. This comprehensive guide will teach you everything you need to know about stone to kg conversions.

The Basic Stone to KG Conversion

The stone is an imperial unit of weight that equals exactly 14 pounds. When converting to the metric system, one stone equals approximately 6.35 kilograms. For most practical purposes, rounding to 6.35 kg is perfectly accurate.

Quick Stone to KG Conversion Chart

How to Convert Stone and Pounds to Kilograms

Most people express their weight in stone and pounds (e.g., "10 stone 7 pounds"). Here's how to convert this to kilograms:

Alternatively, you can use this combined formula:

Why Does the UK Still Use Stone?

The United Kingdom officially adopted the metric system in 1965, yet stone remains the preferred unit for body weight in everyday conversation. There are several reasons for this cultural quirk:

Historical Tradition

The stone has been used in Britain since the 14th century for weighing wool, and later for general commerce. This centuries-old tradition is deeply embedded in British culture.

Convenient Numbers

Stone gives smaller, more manageable numbers than kilograms. Saying "I weigh 11 stone" feels more natural to many Britons than saying "I weigh 70 kilograms."

Generational Habits

Older generations grew up with imperial measurements and passed these habits to their children. While young people may be equally comfortable with kilograms, stone persists in family discussions about weight.

When to Use Stone vs Kilograms

Understanding when each unit is appropriate helps you communicate effectively:

Average UK Weights in Stone and Kilograms

According to NHS data, the average body weights in the UK are:

These averages have increased over the past few decades, making accurate weight tracking more important than ever for health monitoring.

Converting KG to Stone

Sometimes you need to convert in the opposite direction, especially when reading international health guidelines. Here's the formula:

Example: 75 kg ÷ 6.35 = 11.8 stone (11 stone 11 lbs)

Mental Maths Tricks for Quick Conversions

When you need a quick estimate without a calculator, try these mental shortcuts:

Stone to KG (Approximate)

• Multiply stone by 6, then add a bit more
• 10 stone ≈ 60 kg + 3.5 = 63.5 kg
• 12 stone ≈ 72 kg + 4 = 76 kg

KG to Stone (Approximate)

• Divide kg by 6 for a rough stone figure
• 70 kg ÷ 6 ≈ 11.7 stone (actual: 11 stone 0 lbs)
• 80 kg ÷ 6 ≈ 13.3 stone (actual: 12 stone 8 lbs)

Stone Conversions for BMI Calculations

BMI (Body Mass Index) calculations require weight in kilograms. If you know your weight in stone, you'll need to convert first:

For example, someone who is 5'8" (1.73m) and weighs 12 stone (76.2 kg):

BMI = 76.2 ÷ (1.73 × 1.73) = 76.2 ÷ 2.99 = 25.5

Use our BMI Calculator to check your own body mass index.

International Comparisons

The stone is almost exclusively used in the UK and Ireland. Here's how other countries measure body weight:

• USA: Pounds only (e.g., "I weigh 154 pounds")
• Europe: Kilograms
• Australia: Kilograms (though older Australians may remember stone)
• Canada: Mixed - officially metric, but pounds commonly used

Using Our Stone to KG Calculator

For accurate, instant conversions, our online calculator handles all the maths for you. Simply enter your weight in stone and pounds, and get the exact kilogram equivalent. It works both ways, so you can also convert kg back to stone.

Conclusion

While the UK officially uses the metric system, stone remains a beloved unit for measuring body weight. Understanding how to convert between stone and kilograms is essential for health tracking, international travel, and communicating with healthcare professionals.

Remember: 1 stone = 6.35 kg, and our free calculator is always here when you need a precise conversion.

The History of the Stone as a Unit of Weight

The stone has a remarkably long history in the British Isles, stretching back to at least the early medieval period. The word itself is thought to derive from the ancient practice of using actual stones as counterweights in balance scales. Before standardisation, the size of a stone varied dramatically depending on the commodity being weighed and the region. A stone of wool in London differed from a stone of cheese in Suffolk, and both differed from a stone of hemp or flax.

It was Edward III who first standardised the stone of wool at 14 pounds in 1340, establishing a figure that would eventually become universal. The Weights and Measures Act of 1824 formally defined the stone as 14 avoirdupois pounds across the entire United Kingdom, putting an end to centuries of regional variation. Despite the Weights and Measures Act 1985 officially removing the stone as a unit of trade, it was granted continued informal use for describing personal body weight, a concession that reflects how deeply embedded the unit is in British and Irish culture.

Today, the stone is practically unique to the UK and Ireland. Even countries that once shared the British imperial system, such as Australia, Canada, and South Africa, abandoned the stone when they fully metricated during the twentieth century. The continued British attachment to the stone is often cited as one of the most distinctive quirks of the UK's measurement practices.

NHS BMI Guidelines Using Stones

The National Health Service calculates Body Mass Index using kilograms and metres, but recognises that most British patients think in stones and pounds. The NHS BMI healthy weight calculator on nhs.uk allows users to enter their weight in either unit system. BMI categories as defined by the NHS are as follows:

• Underweight: BMI below 18.5
• Healthy weight: BMI 18.5 to 24.9
• Overweight: BMI 25 to 29.9
• Obese: BMI 30 or above

To illustrate what these categories mean in practical stone-to-kg terms, consider a person who is 5 feet 6 inches tall (168 cm). Their healthy weight range is approximately 8 stone 3 pounds to 10 stone 12 pounds (52 kg to 69 kg). Reaching a BMI of 25 (the overweight threshold) would occur at roughly 10 stone 13 pounds (69.4 kg), while a BMI of 30 (obese) would be reached at approximately 13 stone 2 pounds (83.5 kg). The NHS recommends that individuals aiming to lose weight do so at a rate of no more than 1 to 2 pounds per week, which is equivalent to losing roughly one stone every two to three months.

Airline Baggage Limits: Stone to KG in Practice

One of the most common situations where British travellers need stone-to-kg conversions is when packing for a flight. All airlines operating from UK airports set luggage allowances in kilograms. Typical allowances from major UK airlines include:

• Cabin baggage: 7 to 10 kg (approximately 1 stone 1 pound to 1 stone 8 pounds)
• Checked hold luggage (short-haul economy): 15 to 23 kg (approximately 2 stone 5 pounds to 3 stone 9 pounds)
• Checked hold luggage (long-haul economy): 23 to 32 kg (approximately 3 stone 9 pounds to 5 stone 0 pounds)
• Business and first class: 32 to 46 kg (approximately 5 stone 0 pounds to 7 stone 3 pounds)

Being able to quickly estimate whether your suitcase is within limits using a stone-based mental reference can save you from excess baggage charges at the airport. If you own bathroom scales that only display stone and pounds, you can weigh yourself holding the suitcase and then without it, convert the difference to kilograms, and check against your airline's allowance.

Frequently Asked Questions

Is the stone still a legal unit of measurement in the UK?

The stone is no longer a legal unit for trade purposes under the Weights and Measures Act 1985. You will not see goods sold by the stone in shops, and businesses cannot use it on product labels. However, it remains perfectly legal to use the stone informally, and it continues to be widely used in everyday conversation, on bathroom scales, and in media references to body weight. The UK government has not attempted to ban informal use of the stone, recognising its cultural significance.

Why do NHS scales show kilograms if most patients think in stones?

Medical equipment in the UK is calibrated in kilograms because clinical guidelines, drug dosages, and anaesthetic protocols are all calculated in metric units. Using kilograms reduces the risk of dosage errors that could occur from converting between measurement systems. Doctors and nurses routinely convert the kilogram reading into stones and pounds when discussing weight with patients, and many clinic scales have a dual display showing both units simultaneously.

How do I convert my luggage weight from stone to kilograms for a flight?

Multiply the stone value by 6.35 and add any remaining pounds multiplied by 0.454. For a quick mental estimate, multiply the stone figure by 6 and add a little extra. For example, if your suitcase weighs 3 stone 4 pounds, the calculation is (3 x 6.35) + (4 x 0.454) = 19.05 + 1.82 = 20.87 kg, which would be within a standard 23 kg checked luggage allowance. Alternatively, use our free online converter for an instant result.