Pounds to Stones Converter

The pound (lb) and the stone (st) are both avoirdupois units used for body weight in the UK and Ireland. One stone = exactly 14 pounds, a relationship that has been British statute since the Weights and Measures Act 1985 (and customary law since the 14-pound wool stone of 1350 under Edward III). One pound = exactly 0.45359237 kilograms, fixed by the international yard-and-pound agreement of 1 July 1959 among the US, UK, Canada, Australia, New Zealand and South Africa. Therefore one stone = 14 × 0.45359237 = 6.35029318 kg (exact).

This converter works in both directions: enter stones and pounds in the two boxes to see the total in pounds, kilograms, grams, ounces and US short tons; or use it as a pure pounds-to-stones calculator and read the result in the canonical UK form (e.g. "11 st 4 lb" not "158 lb"). The math is exact, no rounding other than what's displayed, so the output is suitable for medical records, parcel-shipping weight brackets, sports weight-classes (boxing, wrestling, horse racing, rowing eights) and any professional or commercial use.

How to Use

1. Stones (st), enter the whole-stone part of the weight. UK body weight is usually quoted as "X st Y lb" so the integer part goes here. Use 0 if you want to convert a pure pounds value.
2. Pounds (lb), enter the remaining 0 to 13 lb. The converter accepts decimal pounds (e.g. 4.5 lb for "4 lb 8 oz") but the canonical UK form uses whole pounds.
3. The result block shows the total in pounds (so 11 st 4 lb = 158 lb), the canonical UK form (11 st 4 lb), and kilograms (71.66879 kg rounded). Bonus read-outs give grams, US ounces (1 lb = 16 oz) and US short tons (1 ton = 2000 lb).
4. Use the presets for common body weights, 8 st (light), 10 st (average UK adult female), 11 st 4 lb (average UK adult male), 14 st (heavy), 20 st (clinical). Click a preset to populate the inputs.

The Formulae

The conversion rests on two exact definitions:

1 lb (avoirdupois) = 0.45359237 kg          (international agreement, 1959)
1 st (stone)       = 14 lb                  (UK Weights and Measures Act 1985)
1 st               = 14 × 0.45359237 kg
                   = 6.35029318 kg          (exact, no rounding)
1 lb               = 16 oz (US avoirdupois)
1 US short ton     = 2000 lb

To go from stones + pounds to total pounds:

total_lb = stones × 14 + pounds

To go from pounds to stones + pounds (canonical UK form):

whole_stones = floor(total_lb / 14)
remainder_lb = total_lb − whole_stones × 14

To go from stones + pounds to kilograms:

kg = (stones × 14 + pounds) × 0.45359237

And back:

st = kg / 6.35029318
lb = kg / 0.45359237

The factor 6.35029318 kg/st is exact, no rounding error accumulates. Display rounding is 5 decimal places by default, which is more precise than any bathroom scale.

Worked Examples

Example 1, 11 st 4 lb (average UK adult male):

• total_lb = 11 × 14 + 4 = 154 + 4 = 158 lb
• kg = 158 × 0.45359237 = 71.66759446 kg ≈ 71.66759 kg
• g = 71,667.59 g (rounded)
• oz = 158 × 16 = 2,528 oz
• US short tons = 158 / 2000 = 0.079 ton

Example 2, 10 st (average UK adult female):

• total_lb = 10 × 14 = 140 lb
• kg = 140 × 0.45359237 = 63.50293180 kg ≈ 63.50293 kg
• oz = 140 × 16 = 2,240 oz

Example 3, 14 st 0 lb (a "14-stone person"):

• total_lb = 14 × 14 = 196 lb
• kg = 196 × 0.45359237 = 88.90410452 kg ≈ 88.90410 kg

Example 4, 1 pound, working backwards:

• 1 lb = 1 / 14 st = 0.0714285714… st (repeating decimal; canonical form is "0 st 1 lb")
• 1 lb = 0.45359237 kg
• 1 lb = 16 oz

Example 5, 1 kg, working backwards:

• 1 kg = 1 / 0.45359237 lb = 2.2046226218… lb
• 1 kg = 1 / 6.35029318 st = 0.1574730444… st
• canonical UK form: 0 st 2.2046 lb (or 0 st 2 lb 3.27 oz)

Example 6, 224 lb (boundary case: 16 st exactly):

• total_lb = 224
• 224 / 14 = 16 exactly, remainder 0
• canonical UK form: 16 st 0 lb
• kg = 224 × 0.45359237 = 101.60469088 kg ≈ 101.60469 kg

Example 7, 0 lb (edge case):

• 0 lb = 0 st 0 lb = 0 kg = 0 g = 0 oz

Example 8, Half-stone (7 lb):

• 7 lb = 0.5 st exactly
• 7 lb = 3.17514659 kg
• canonical UK form: 0 st 7 lb

Example 9, 12 st 8 lb (an athlete's weight):

• total_lb = 12 × 14 + 8 = 168 + 8 = 176 lb
• kg = 176 × 0.45359237 = 79.83225712 kg ≈ 79.83226 kg

Example 10, 20 st (clinical threshold):

• total_lb = 20 × 14 = 280 lb
• kg = 280 × 0.45359237 = 127.00586360 kg ≈ 127.00586 kg

Where It Shows Up

• Body weight in the UK and Ireland, most British adults quote their weight in stones and pounds, not in pounds or kilograms. Doctors' notes, prescription charts, hospital wristbands and weight-loss programmes use "st lb" canonically.
• Boxing weight classes, British boxing still uses stones for some amateur divisions; "11 st 4 lb" was historically a common middleweight threshold.
• Wrestling, horse racing, rowing, some traditional British sports still record weights in stones; a rowing "eight" crew member might be listed at "12 st 6 lb".
• Parcel and freight shipping, international carriers convert between kg and lb constantly; UK domestic services sometimes still accept stones for very heavy items (e.g. building materials, animal feed).
• Recipe and grocery contexts in older UK cookbooks, pre-1970s British recipes often quote ingredient weights in pounds and ounces; modern converters like this one are essential for translating.
• Agricultural and livestock contexts, Ireland still uses stones for cattle and sheep weights at smaller markets, even though the official metric unit is kg.
• Personal fitness apps with UK user bases, most cross-platform apps (Strava, MyFitnessPal UK region, Apple Health set to stones) display body weight in stones + pounds and need a reliable conversion to kg for storage.
• Medical dosing and pharmaceutical compounding, UK clinical pharmacists sometimes still receive patient weights in stones from older GPs; conversions to kg are needed for mg/kg dosing calculations.

Common Mistakes

1. Confusing the international pound (0.45359237 kg) with the older "metric pound" of 500 g, the metric pound was an informal unit used briefly in the 19th century; modern statute (UK, US, Commonwealth) uses the international pound only. This converter uses 0.45359237 kg exactly.
2. Using 14 lb when the source actually means 16 lb, historically some US sources used a "stone" of 16 lb for specific goods (e.g. wool in some colonies). The UK statute fixes 14 lb; this converter uses that.
3. Rounding 1 st to "6.35 kg", the exact value is 6.35029318 kg; rounding to two decimals (6.35) introduces ~0.029 kg error per stone, which accumulates for heavier people. This converter displays 5 decimal places by default.
4. Treating "stones and pounds" as an arithmetic sum of two separate fields, when entering "12 st 8 lb", the 8 lb is the remainder after subtracting whole stones; not a separate independent weight. The converter handles this correctly.
5. Forgetting that US medical scales report pounds, not stones, Americans often misread "11 st" as "11 pounds" or "11 kg". This converter assumes you've entered stones (not pounds) in the first field.
6. Using the troy pound (5,760 grains = 0.3732417216 kg) for body weight, the troy pound is for precious metals and pharmaceuticals, not people. This converter uses the avoirdupois pound (7,000 grains = 0.45359237 kg).
7. Assuming "stones and pounds" is the same in Ireland and the UK, both use the same definitions; the difference is only that Ireland formally uses metric (kg) for trade while still colloquially using stones for body weight. The conversion factors are identical.

Frequently Asked Questions

How many pounds are in a stone? There are exactly 14 pounds (avoirdupois) in one stone, by the UK Weights and Measures Act 1985. This is the only definition recognised for trade in the UK and Ireland. The relationship dates to the 14-pound wool stone fixed by statute in 1350 under Edward III.

How many kilograms are in a stone? One stone = 6.35029318 kg, exactly. This follows from the international yard-and-pound agreement of 1 July 1959, which fixed the pound at 0.45359237 kg, combined with the UK statutory definition of the stone as 14 pounds: 14 × 0.45359237 = 6.35029318 kg.

How do I convert stones to kg manually? Multiply stones by 14 to get total pounds, then multiply by 0.45359237 to get kg. Formula: kg = stones × 14 × 0.45359237 = stones × 6.35029318. Example: 11 st = 11 × 6.35029318 = 69.85322 kg (rounded).

How do I convert pounds to stones? Divide pounds by 14. The integer part is the whole stones; the remainder (0 to 13.999…) is the leftover pounds. Formula: stones = floor(lb / 14); remainder_lb = lb − stones × 14. Example: 158 lb ÷ 14 = 11 remainder 4, so "11 st 4 lb".

What is the difference between the UK stone and the US stone? The US does not formally use the stone as a unit. Some US contexts (boxing weight classes, recipe conversions) borrow the UK 14-pound stone for convenience, but it's not a US statutory unit. This converter uses the UK definition throughout.

Why do British people use stones for body weight? The stone was the traditional English unit of weight (originally a stone of wool = 14 lb, fixed by law in 1350). Even after metrication in the 1970s and 1980s, the stone survived as the colloquial unit for body weight in the UK and Ireland, partly because "11 st 4 lb" feels more natural to a British ear than "70 kg" or "158 lb" when describing a person's size.

Is the stone used in Ireland? Yes. Ireland shares the UK definition (1 st = 14 lb) by virtue of the Metric Act 1967 and historical continuity. The stone is colloquial for body weight in Ireland, even though metric is the formal system for trade.

How accurate is this converter? Mathematically exact at the 6.35029318 kg/st level. Display rounding is to 5 decimal places for kilograms (about 0.00001 kg = 0.01 g precision), which is finer than any practical use. All definitions (lb, st, kg) are taken from the UK statute and the international agreement, no approximation.

Can I use this for medical or pharmaceutical purposes? The conversion is mathematically exact and uses authoritative sources (UK Weights and Measures Act 1985, international yard-and-pound agreement 1959, NIST SP 811). For medication dosing, always verify with a clinician and follow the dose calculation as written in the prescription, some drugs use ideal body weight (IBW) or adjusted body weight rather than total body weight, and this converter does not compute those.

What's the heaviest "stone" weight a person has been recorded at? The heaviest medically validated adult human weight on record is around 635 kg (1,400 lb ≈ 100 st), recorded by Jon Brower Minnoch (USA, 1978). Converted: 1,400 lb ÷ 14 = 100 st exactly. This converter handles any non-negative input.

Why does the converter show both kg and pounds? Body weight in the UK is canonically given in stones and pounds, but most international scientific, medical, and commercial contexts require kilograms. Showing both lets users verify their own knowledge ("I know I weigh about 70 kg, does the stone-and-pound version match?") and use the result in any downstream application without an extra conversion step.

can the Pounds to Stones Converter, UK Body Weight (14 lb / st) be used for professional or commercial purposes? yes, the Pounds to Stones Converter, UK Body Weight (14 lb / st) provides mathematically correct results that are suitable for professional, commercial, and educational use. For the Pounds to Stones Converter, UK Body Weight (14 lb / st), For the Pounds to Stones Converter, UK Body Weight (14 lb / st), For high-stakes applications (medical, legal, financial), verify results with a domain expert. For the Pounds to Stones Converter, UK Body Weight (14 lb / st), the Pounds to Stones Converter, UK Body Weight (14 lb / st) formulas used are well-established and validated against reference standards.

For the Pounds to Stones Converter, UK Body Weight (14 lb / st), How often are the underlying formulas updated? For the Pounds to Stones Converter, UK Body Weight (14 lb / st), the Pounds to Stones Converter, UK Body Weight (14 lb / st) formulas are based on established scientific, mathematical, or industry-standard references and rarely require updates. When standards change (e.g., new physical constants, revised tax brackets, updated standards), the Pounds to Stones Converter, UK Body Weight (14 lb / st) is updated to reflect the current authoritative source. For the Pounds to Stones Converter, UK Body Weight (14 lb / st), For the Pounds to Stones Converter, UK Body Weight (14 lb / st), Each calculator's references section lists the specific sources used.

References

1. UK Weights and Measures Act 1985 (c. 72), Schedule 1, units of measurement lawfully usable for trade. Published by The Stationery Office, London.
2. International yard-and-pound agreement of 1 July 1959 among the US, UK, Canada, Australia, New Zealand and South Africa, fixed 1 yard = 0.9144 m exactly and 1 lb (avoirdupois) = 0.45359237 kg exactly. Federal Register, US National Archives.
3. For the Pounds to Stones Converter, UK Body Weight (14 lb / st), NIST Special Publication 811 (2008), Appendix B.8, Recommended Conversion Factors for Use by Federal Agencies. National Institute of Standards and Technology, US Department of Commerce.
4. Metric Act 1967 (Ireland), confirms the Irish use of metric units for trade while preserving customary units (including the stone) for colloquial use.
5. The Weights and Measures (Equivalents for Dealing with Drugs) Order 1970 (SI 1970/1897), UK statutory instrument that defines the pound in grams (454 g, rounded) for pharmaceutical contexts.
6. British Pharmacopoeia (current edition), references the international pound and avoirdupois system for pharmaceutical compounding.

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