Stone to Kg Converter UK 2025/26 | Stone & Pounds to Kilograms Calculator

NHS BMI Categories

The NHS uses BMI (Body Mass Index) to assess whether adults are a healthy weight for their height. Here are the standard categories:

Note: BMI is a general guide. It doesn't account for muscle mass, age, gender, or ethnicity. Athletes may have a high BMI but low body fat. Consult your GP for personalized health advice.

Healthy Weight Ranges by Height (UK)

These ranges show healthy weights (BMI 18.5-24.9) for different heights. Use as a general guide only.

Stone to KG Conversion Table

Quick reference table for common stone to kilogram conversions:

KG to Stone Conversion Table

Convert common kilogram weights to stones and pounds:

How to Use the Stone to KG Converter

Enter weight in any field (stones, pounds, or kilograms) and the converter automatically calculates the other units in real-time. For stone to kg: enter stones and pounds separately. For kg to stones: the result shows full stones plus remaining pounds. Conversions are based on official UK measurement standards: 1 stone = 14 pounds = 6.35029 kilograms exactly.

Conversion Formulas

Stones to Kilograms

Example: 10 stone = 10 × 6.35029 = 63.5 kg

For stones and pounds: divide pounds by 14 to get stone fraction, add to whole stones, then multiply by 6.35029.

Example: 10 stone 7 pounds = (10 + 7÷14) × 6.35029 = (10 + 0.5) × 6.35029 = 66.68 kg

Kilograms to Stones and Pounds

Example: 70 kg ÷ 6.35029 = 11.024 stone

To convert decimal to pounds: multiply by 14. Example: 0.024 × 14 = 0.34 pounds, so 70 kg = 11 stone 0.3 pounds.

Why UK Uses Stones

Stone has been used in Britain since the 1300s for weighing goods and livestock. The imperial system standardized 1 stone = 14 pounds in 1389. Despite UK officially adopting metric system in 1965 for trade, stones remain dominant for body weight due to cultural tradition.

Most UK bathroom scales show both stones/pounds and kilograms. NHS uses both units in health guidance. Only UK and Ireland use stones regularly - rest of world uses kilograms exclusively for body weight.

Stone: A Uniquely British Measurement

The stone is one of the most distinctly British units of measurement still in common use. While the rest of the world moved to kilograms decades ago, the stone remains deeply woven into British culture, language and daily life. Understanding its history helps explain why UK residents still think about body weight in stones rather than kilograms.

Origins and History of the Stone

The word "stone" as a unit of weight dates back to at least the early medieval period. Before standardised weights existed, traders used actual stones as counterweights on balance scales. Different regions used different sized stones, leading to considerable confusion. In the wool trade alone, a "stone" could mean anything from 5 to 32 pounds depending on the locality and the commodity being weighed.

The situation was resolved in 1389 when a royal statute under King Edward III fixed the stone at exactly 14 pounds avoirdupois. This standardisation was primarily driven by the wool trade -- England's most important export at the time. The 14-pound stone became the universal standard and has remained unchanged for over 600 years.

The Metrication of Britain

In 1965, the UK government announced that Britain would adopt the metric system for trade and commerce. The Metrication Board was established in 1969 to oversee the transition. By the 1980s, most goods were sold in metric units (litres, kilograms, metres). However, the transition was never fully completed:

• Road signs remain in miles and mph
• Pints are still used for beer and milk
• Body weight is still discussed in stones and pounds by most British people
• Height is typically given in feet and inches in everyday conversation

The Weights and Measures Act 1985 permitted the use of supplementary imperial indications alongside metric, ensuring that stones could legally continue alongside kilograms. Today, the stone occupies a unique position: officially superseded by the kilogram but culturally dominant for body weight in the UK.

Stone in Modern British Culture

If you ask a British person how much they weigh, they will almost certainly answer in stones and pounds. This cultural habit crosses all age groups, social classes and regions. British media -- newspapers, magazines, TV programmes -- overwhelmingly report body weight in stones.

Slimming clubs like Weight Watchers and Slimming World operate in stones in the UK. Even UK-sold bathroom scales typically display both imperial (stone/lbs) and metric (kg) readings, with the stone scale often being the default.

The stone also features in everyday British expressions: "half a stone" (7 lbs / 3.18 kg) is a common target for weight loss, and descriptions like "she lost two stone" are immediately understood across the UK.

How Other Countries Abandoned the Stone

Several former British colonies used the stone historically but abandoned it during metrication. Australia completed its switch to metric in the 1970s and within a generation, Australians thought exclusively in kilograms. Canada followed a similar path, officially converting in the 1970s-80s, though some older Canadians still remember stone. New Zealand adopted metric in 1969 and the stone quickly fell out of use. South Africa metricated in 1971. The United States never used stone at all, having adopted the pound as its primary weight unit from independence. Today, only Britain and Ireland retain the stone for everyday body weight, making it one of the most geographically limited units of measurement still in active use.

Stone in Sport and Athletics

British sport has a complex relationship with the stone. In boxing, weight classes have traditionally been described in stones and pounds in the UK (e.g. "middleweight" at roughly 11 stone 6 lbs) though international boxing bodies use kilograms and pounds. Horse racing in the UK still uses stones and pounds for jockey and horse weights -- a tradition dating back centuries. Rugby and cricket in England typically report player weights in stones in British media but in kilograms for international contexts. Meanwhile, athletics, weightlifting and Olympic sports use kilograms exclusively worldwide, including in the UK.

Stone to Kg in UK Healthcare

Understanding the relationship between stone and kilograms is particularly important in a healthcare context. The NHS (National Health Service) operates exclusively in metric units for clinical purposes, yet most British patients think about their weight in stones.

Why the NHS Uses Kilograms

All NHS clinical systems record weight in kilograms for several important reasons:

• Drug dosages are calculated per kilogram of body weight (e.g. mg/kg). Using stones would introduce dangerous conversion errors.
• BMI calculations use the formula weight (kg) / height (m) squared -- metric throughout.
• International medical research and guidelines use kilograms exclusively.
• Electronic health records (such as the NHS Spine) store weight in kilograms for consistency.
• Anaesthetic dosing is critically dependent on accurate weight in kilograms.

The Communication Gap

Despite recording weight in kilograms, NHS staff frequently encounter patients who only know their weight in stones. A 2019 study found that roughly 65% of UK adults could state their weight in stones but only 35% could state it accurately in kilograms. This creates a practical communication challenge:

• GP receptionists often ask weight in stones and convert before entering it into the system
• Hospital admission forms may include fields for both stones and kilograms
• NHS health advice pages (such as the NHS BMI calculator) accept input in both units
• Midwives and health visitors typically discuss baby weight in both pounds/ounces and kilograms

If you are attending an NHS appointment and need to know your weight in kilograms, our stone to kg converter above provides the exact conversion you need.

Prescriptions and Drug Dosages

One of the most critical reasons the NHS uses kilograms is medication dosing. Many drugs are prescribed in milligrams per kilogram of body weight (mg/kg). For example, paracetamol for children is dosed at 15 mg/kg per dose.

If a parent tells a pharmacist their child weighs "3 stone 2 pounds" (20 kg), the pharmacist must convert to kilograms before calculating the correct dose. Errors in weight conversion can lead to under-dosing (ineffective treatment) or over-dosing (potentially dangerous). This is why accurate stone to kg conversion is not merely convenient -- it can be medically important.

Weight Management and the NHS

The NHS provides comprehensive weight management guidance through programmes like the NHS Better Health campaign. When setting weight loss targets, NHS advisors often work in both units -- discussing targets in stones (which patients understand) whilst recording progress in kilograms (which the clinical system requires). A typical NHS weight loss recommendation of 5-10% of body weight translates to roughly half a stone to one stone for an average adult.

Stone to Kg for Children and Young People

Children's weight in the UK is measured in kilograms from birth. The NHS red book (Personal Child Health Record) uses kilogram-based growth charts. However, as children grow into teenagers, many British families begin discussing weight in stones -- the same unit their parents use.

This transition typically happens around age 10-13. School nurses and GPs continue to use kilograms throughout, creating the same communication gap seen in adult healthcare. The National Child Measurement Programme (NCMP), which weighs children in Reception (age 4-5) and Year 6 (age 10-11), records all data in kilograms. Parents receive results showing both kg and an approximate stone/pound equivalent to aid understanding.

Complete Stone to Kg Conversion Table (1-30 Stone)

This comprehensive table shows stone and pound combinations converted to kilograms. Each stone is broken down into 0, 7 and full 14-pound subdivisions for quick reference. All values are calculated using the exact conversion factor: 1 stone = 6.35029 kg.

When You Need to Convert Stone to Kg

There are many everyday situations in the UK where knowing your weight in both stones and kilograms is essential. Here are the most common scenarios:

Medical Appointments

When visiting your GP, hospital or any NHS facility, your weight will be recorded in kilograms. If you are asked to provide your weight over the phone or on a form, knowing the kilogram equivalent of your stone weight avoids delays and potential errors. This is especially important for:

• Pre-operative assessments where anaesthetic doses depend on accurate kg weight
• Pregnancy check-ups where weight gain is monitored in kilograms
• Chronic disease management (diabetes, heart disease) where weight targets are set in kg
• Paediatric appointments where child growth charts use kilograms

Gym and Fitness

Most gym equipment in the UK -- weight machines, dumbbells, barbells and plate-loaded equipment -- is labelled in kilograms. If you set a weight loss or muscle gain target in stones, you need the kg conversion to track progress on gym equipment. Many fitness apps and wearable devices (Fitbit, Apple Watch, Garmin) default to kilograms, so entering your weight in kg ensures accurate tracking of calories burned, BMR calculations and body composition analysis.

Travelling Abroad

If you travel outside the UK and Ireland, nobody will understand your weight in stones. European countries, Asian countries, African countries and South American countries all use kilograms exclusively. Even in the United States, stone is not used -- Americans measure body weight in pounds only. Knowing your weight in kilograms is essential for:

• Medical emergencies abroad where doctors need your weight in kg
• Airline baggage -- some carriers ask for passenger weight in kg for small aircraft
• Adventure activities (bungee jumping, zip lines, skydiving) with kg weight limits
• Buying clothes in countries that use metric sizing

BMI Calculations

The Body Mass Index formula uses kilograms and metres: BMI = weight (kg) / height (m) squared. While our BMI calculator accepts stone input, if you are using any other BMI tool, medical form or health app, you will need your weight in kilograms. The NHS healthy weight range of BMI 18.5-24.9 is calculated entirely in metric units.

Online Shopping and Product Specifications

Weight limits on products sold in the UK are typically stated in kilograms due to EU-origin regulations. Camping chairs, office chairs, ladders, trampolines and mobility aids all state their maximum user weight in kg. Knowing your weight in kilograms helps you choose safe, appropriate products.

Pregnancy and Maternity

During pregnancy in the UK, midwives record maternal weight in kilograms at booking appointments and subsequent visits. Weight gain during pregnancy is monitored against guidelines expressed in kilograms. The NICE (National Institute for Health and Care Excellence) guidelines classify pre-pregnancy BMI -- calculated from weight in kilograms -- to determine the level of additional monitoring needed.

Pregnant women who know their weight only in stones will need to convert to kg for these assessments. Typical healthy pregnancy weight gain is 10-12.5 kg (roughly 1.5 to 2 stone) for women starting at a healthy BMI.

Dieting and Weight Loss Tracking

Many popular diet and nutrition apps -- including MyFitnessPal, Noom, Lifesum and the NHS Weight Loss Plan app -- default to kilograms. While most offer a stone option, some features (such as calorie deficit calculations and projected weight loss timelines) work more accurately in kilograms because the underlying algorithms use metric units. If you set a target of "lose a stone" (6.35 kg), the app needs to convert this internally. Knowing both your stone and kg weight from the start ensures smoother tracking.

Insurance and Financial Services

Life insurance and health insurance applications in the UK typically ask for weight in kilograms, as underwriting systems use metric data. Travel insurance medical declarations may also require your weight in kg. If you are applying for insurance and only know your weight in stones, an inaccurate conversion could affect your application.

Similarly, some workplace occupational health assessments require weight in kilograms for risk assessments related to manual handling, safety equipment fitting and personal protective equipment (PPE) sizing. Having an accurate stone to kg figure ready can streamline these processes considerably.

Stone, Pounds and Kg -- Understanding the Differences

Three different weight units are commonly encountered in the UK, each with its own history, usage context and conversion factors. Understanding the relationships between them is essential for accurate weight conversion.

The Kilogram (kg)

The kilogram is the base unit of mass in the International System of Units (SI). It was originally defined in 1795 as the mass of one litre of water at 4 degrees Celsius. Since 2019, it has been defined by the Planck constant, making it independent of any physical artefact.

The kilogram is used by every country in the world for scientific, medical and commercial purposes. In the UK, the kilogram is the legal unit for trade (since the Weights and Measures Act 1985) and the standard unit in all NHS clinical systems.

The Pound (lb)

The pound avoirdupois is an imperial unit still widely used in the United States and the United Kingdom. 1 pound = 0.453592 kilograms exactly (defined by international agreement in 1959). In the UK, pounds are used alongside stones for body weight (e.g. "11 stone 4 pounds") and for food labelling as a supplementary indication. In the United States, pounds are the primary unit for body weight, with no reference to stones.

The Stone (st)

The stone is an imperial unit equal to exactly 14 pounds or 6.35029 kilograms. It is used almost exclusively in the United Kingdom and Ireland for measuring body weight. The stone is not recognised as a legal unit of measurement for trade under current UK law (the UK government mandates metric units for trade), but it remains in widespread colloquial use. No other country uses the stone as a standard unit.

Why Three Systems Persist in the UK

The UK's use of three weight units simultaneously is a direct result of incomplete metrication. While most countries completed their transition to metric within a single generation, Britain's cultural attachment to imperial units -- combined with a lack of political will to enforce full metrication -- means that British people routinely navigate between systems. A typical UK adult might:

• Weigh themselves in stones and pounds on their bathroom scales each morning
• Have their weight recorded in kilograms at the doctor's surgery
• Read food packaging in grams and kilograms at the supermarket
• Describe a newborn baby's weight in pounds and ounces
• Set a weight target in kilograms on their fitness app
• Discuss their weight loss in stones with friends and family

This multi-system reality makes conversion tools like our stone to kg calculator genuinely useful for everyday life in Britain, not merely an academic exercise.

Common Conversion Mistakes to Avoid

When converting between stone and kilograms, several errors commonly occur:

• Forgetting the pounds: "11 stone 7" is not 11 stone -- the 7 pounds must be included. 11 st 7 lb = 73.03 kg, not 69.85 kg.
• Using an approximate factor: Some people round 6.35029 to 6.35 or even 6.4. Over larger weights, this introduces significant error. At 20 stone, the difference between 6.35 and 6.35029 is 0.06 kg.
• Confusing stone with pounds: In the US, "I weigh 140" means 140 pounds (63.5 kg / 10 stone). In the UK, "I weigh 10" typically means 10 stone (63.5 kg / 140 lbs). Context matters enormously.
• Assuming 10 pounds per stone: Some people mistakenly think there are 10 pounds in a stone (perhaps by analogy with the decimal system). There are 14 pounds in a stone -- always.

Quick Conversion Reference

Sources and Methodology

All conversions on this page use the internationally agreed conversion factors established by the International Yard and Pound Agreement of 1959. Our data and health references come from authoritative UK sources:

• Conversion factor: 1 pound = 0.45359237 kilograms (exact, by international agreement). Therefore 1 stone = 14 x 0.45359237 = 6.35029318 kg.
• NHS healthy weight guidance: NHS Live Well - Healthy Weight -- BMI ranges, healthy weight by height, weight management advice.
• NHS BMI calculator: NHS BMI Calculator -- official BMI calculation tool accepting both stone and kg input.
• UK metric measurement guidance: GOV.UK - Using Metric Measurements -- official government guidance on legal units of measurement in the UK.
• Average UK weight data: NHS Health Survey for England -- published annually, providing population-level weight and BMI statistics.
• Weights and Measures Act 1985: The UK legislation governing legal units of measurement for trade and commerce.

This calculator is updated regularly and was last verified on 2 March 2026. The mathematical conversion factors are constants and do not change.

How We Ensure Accuracy

Our stone to kg converter uses the exact conversion factor of 1 avoirdupois pound = 0.45359237 kilograms, which was established by the International Yard and Pound Agreement signed in 1959 by the United States, United Kingdom, Canada, Australia, New Zealand and South Africa. This is not an approximation -- it is a definition. From this definition, 1 stone = 14 x 0.45359237 = 6.35029318 kilograms exactly.

We display results to two decimal places for practical use, though the underlying calculation uses full precision. Our BMI calculator uses the same conversion factor, ensuring consistency across all our weight-related tools. We regularly cross-check our results against the NHS and gov.uk published conversion references to ensure ongoing accuracy.

Related UK Weight and Health Calculators

Use these related calculators alongside our stone to kg converter for a complete picture of your weight and health metrics:

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